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Hot dip galvanizing flux

adv. pointer 

     
++++++

Q. Dear Dr. Cook,

I have read the valuable suggestions you give to various galvanisers and here I would like to take this opportunity to get your advice. We galvanize tubes. presently, we are facing problems in getting the right quality of flux. can you please advice us the process and the formulation so that we can prepare our own quality flux based on triple salt.

Regards,

Rajiv Shah
pipe manufacturer - Hyderabad, India


++++++

A. Dear Rajiv,
Triple Salt is 54% Ammonium Chloride and 46% Zinc Chloride. This is an "ACN" (Ammonium Chloride Number of 1.17; which is the weight of ammonium chloride divided by the weight of zinc chloride; e.g. ACN of triple salt = 54/46). If you strongly heat the pipes after fluxing then the double salt is more thermally stable with an ACN of 0.8. If you only slightly heat the pipes after fluxing then quadraflux with an ACN of 1.6 is good. Quadraflux has the advantage of producing thinner and smoother zinc coatings on the inside of the pipes. A certain wetting agent produced only in the USA and Germany is the only one that I have found works well in galvanizing fluxes.
Thank you for asking me your question. You could get additional information from my journal articles in Metal Finishing.
Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota


+++++++

A. Flux solutions should be kept on 50 degrees to perform well.

Sondergaard
- Denmark


+++++++

A. Dear Sondergaard,
It is true that many automatic pipes galvanizers use 50° C. and high baume'(density)flux solution for galvanizing medium and small diameter pipes. If the flux solution is hotter, then the last pipes in the bundle will have corrosion lines on the outside and have "black" (bare) spots. (Higher flux temperature causes faster corrosion.) If however, large diameter pipes are galvanized or the "breaking table" is wide enough and slanted such that a single layer of pipes results (for the fluxed pipes), then low baume' and hot flux gives a better result. Better by having a thinner zinc layer on the inside of the pipes and having much less ash (skimmings) at the kettle.
For general galvanizing it is common practice in North America to use either triple salt flux (ACN=1.17) or quadraflux (ACN=1.60) at about 13 to 14 degrees baume' and 71° C. (160° F.). (ACN = weight of ammonium chloride/weight of zinc chloride.) This often gives a percent gross zinc usage between 4% and 5% (%GZU = zinc consumed/steel galvanized all times 100%) (no zinc credits for ash or dross). The correct pH and the proper wetting agent (surfactant) in the flux also help prevent corrosion of the fluxed steel.
Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota


What is Quadraflux?

+++++++

Q. Sir,

I read the name quadraflux during the course of above discussion. I want to know what is quadraflux and what is triple salt flux. Currently I am using flux which is mixture of Ammonium chloride and zinc chloride. Is it called double salt flux. Do triple salt and quadraflux give better result in terms of surface finish and zinc consumption?

Regards

Atul Mishra
Pipes manufacturing - Anjar, Gujrat, INDIA


+++++++

A. Dear Atul,
Galvanizing Fluxes Are:

   Name       Formula     ACN   Uses
Monosalt ZnCl2.NH4Cl 0.4 Sheet
Double Salt ZnCl2.2NH4Cl 0.8 Preheater Gen. Pipes
Triple Salt ZnCl2.3NH4Cl 1.17 Dryer Gen. Pipes
Quadraflux ZnCl2.4NH4Cl 1.6 Gen. Pipes

Many pipe galvanizers use double salt with starting ACN=0.8. In doing rework zinc is stripped into the flux and the ACN goes down as the pH goes up. Over time these out-of-balance conditions interfere with fluxing action. Flux function can be restored with proper amounts of hydrochloric acid and ammonium chloride. This is true of all fluxes.

Pipe galvanizers often use high baume' double salt and get thick zinc coatings on the pipes, particularly on the inside diameters (as much as 200 to 1000 microns). With quadraflux the i.d. zinc coatings are much thinner (as little as 20 to 40 microns). To use low baume' quadraflux the proper equipment after fluxing which includes a broad, tilted "breaking table," walking beam transport, and suitable zinc immersion device (like progressive screws)are required.

For pipe galvanizing, quadraflux is highly successful in South Africa, Southern India, and the USA. It has not been successful in South America and Central India. Proper equipment is essential.

For general galvanizing, the double salt is widely used in Europe (along with preheaters), whereas in the USA triple salt and quadraflux are widely used (no preheaters) at 71 deg. C.
With proper equipment and flux maintenance, YES, quadraflux does give a higher quality product and much less zinc is consumed. I have published a comprehensive article in the journal Metal Finishing regarding quadraflux and you can get it off the internet.

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota

+++++++

Q. Thank you Dr. Cook for your comprehensive reply.

I think by "breaking table" you mean skid or stand before dryer where bundle is kept after fluxing and feeding in to the dryer. We do not have walking beam type conveyor but chain conveyor and pneumatic cylinder (Plunger Type) dipping flux. Should I adopt quadraflux since I cannot change the equipment?

Regards,

Atul Mishra (returning)
Pipes manufacturing - Anjar, Gujrat, INDIA


+++++++

A. Dear Atul,
The breaking table is indeed the stand for the fluxed pipes prior to the dryer. The real question here is if the flux is scratched off the pipes prior to entry into the zinc. If the equipment and the pipes do not rub too much then quadraflux at rather low baume' may work for you. Certainly I cannot advise without seeing how the equipment handles the pipes. For small diameter pipes a progressive screw zinc entry is by far the best way to put the pipes into the zinc. A push down device can allow the pipes to bob up causing black (bare) spots. A progressive screw is strictly one way and that is INTO the zinc. Bending of the pipes during entry is also a problem well known to you.
Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota


+++++++

thumbsup2Dr.T,
What we really NEED is a Seminar organised by you in India (a 3 Day Workshop?).

Regards,

Vipul Tewari
- Kolkata (Calcutta), West Bengal, India


August 9, 2008

Q. Doctor cook
I want to ask is there any chemical which can be used before galvanization with flux or even alone so that
1. It will enhance & intensify surface chemistry
2. It will strengthen the contact bond of interfaces during the process as the iron and zinc combine to form an intermetallic compound at the surface
3. It will heighten the catalytic property of the flux by reducing the surface tension between interfaces.
4. It will let the metal to attain the highest Galvanic protection with zinc by reducing interfacial tension under basic chemical mechanism.

Rahul Sidher
- Hisar Haryana India



July 30, 2009

Q. Kind Attn: Dr. Thomas H. Cook

Dear Sir,

We got the good knowledge of your suggestion regarding Galvanizing Flux; but still we are facing some problem regarding fluxes.
We are manufacture of Galvanizing flux in India. We have hot dip galvanizer customers in India, they are manufacture of transmission tower & we are supplying galvanizing flux to them, but we are not able to satisfy their quality of flux.

As you suggest in above conversation regarding wetting agent(surfactant) in the flux. We want to try this also, for that we want to know the correct name of the wetting agent (surfactant) and the process. So we can satisfy our valuable customers.


Regards,

Vijay K, Limbachia
- Mumbai, Maharashtra, India


July 22, 2010

Q. Sir,
what is the function of BLANKET FLUX in hot dip galvanizing process?

Arpan Mallik Mallik
Trainee quality engg - Kolkata, West Bengal, India


March 2, 2012

Q. Dr. Cook,
I have read your immensely helpful paper on galvanizing flux. I am currently puzzled by a few things, however. I would very much appreciate if you could give me an answer to these:
1. For quadraflux, the baume range is quite small and as you have mentioned can go up with use. How do I control the rise of the density?
2. What would be the best indicator to tell me at what pH my bath is?
Much appreciated.

Tatyana M.
- Canada


March 7, 2012

A. Sir:

To your first question--- The baume' of the flux likely increases because rework or racking fixtures with zinc on them, or spin baskets (to be stripped) are put into the flux and some zinc dissolves causing the baume' to rise. If needed some flux should be taken out and water added. In this stripping process the baume' rises, the pH rises (counter balanced to some extent by acid carry through of the acid rinse), and the ACN drops. Thus the ability to correct for baume' changes, pH changes, and ACN changes are all three required.

To your second question--- The pH testing and control are consulting matters. This Sunday March 11, 2012 I go consulting to three plants and will install the required testing and control equipment, along with other things.

It would be interesting to know what part of Canada you are residing in.

I presume the article you are referring to is the one with the title like: "Testing and Control of Hot Dip Galvanizing Flux" in Metal Finishing?

Regards.

Dr. Thomas H. Cook
- Hot Springs, South Dakota


March 12, 2012

thumbsup2Dr. Cook,

Thank you for the answers. Indeed that was the paper that I have studied. I am writing to you from Scarborough area in Toronto. Currently I am looking to see how I can make maintenance of the quadraflux bath easier (stretching the Baume range by adding wetting agents?).

Tatyana M. [returning]
- Canada, Toronto



Compensating for Fe Concentration When Analyzing Flux

March 15, 2012

Q. In considering flux, and analysis of it, what correction should be applied to measured density to compensate for Fe concentration.

If measuring flux density to ensure correct strength, in a solution with high [Fe], say 2-4% that some operate at, what correction gives a density that simulates 0% Fe?

Geoff Crowley Geoff Crowley
galvanizing &
   powder coating shop
Glasgow, Scotland


March 18, 2012

A. Geoff:

2% to perhaps 4% iron (Fe+2) in the flux likely increases the baume' by about 2 units. I rarely consider this and have found the best baume' in most cases to be near 13 for quadraflux, and temp. of 71 C. Keep in mind that the original concept of ACN was ammonium chloride as numerator and zinc chloride as denominator. With higher dissolved iron a better concept (ACNV) is to have ammonium chloride as numerator and the zinc chloride plus iron (II) chloride as denominator.

I am now at a site where there are many things I do not like including dirt floors and dirt packed tight against the sides of heated caustic, sulfuric acid, and flux tanks. This causes the heat to go into the ground. This location will be a difficult one. They also use carbon-stick heaters which combust under the solution in the tank, without using suds (causes double the heat bill).

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota


March 2012

! I am on a trip in Eastern USA. The baume' of the flux here is now 14.5. I would rather have it 13.

Three days ago the ACN was 1.0, then 1.2 and today 1.4 (just now being tested here in the plant). I may raise it to 1.6 tonight. Going from 1.2 to 1.4 ACN gave much better zinc drainage at the kettle and the icicles are now thin like a foil gum wrapper, whereas yesterday they were still like a pencil point.

The flux required 10 gallons of conc. HCl to attain the proper pH of 4.2 the first day. Yesterday it required 4 gallons of HCl. The test today shows the pH is correct. Thus the flux side is good.

I am doing some other things with excellent results, giving absolutely NO BLACK SPOTS whatsoever and the product is very bright indeed.

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota


May 3, 2012

Q. Dr. Cook,
We do 2000 tons of angle galvanizing every month. We use pre-flux bath followed by dryer followed by galvanizing. We are not using any ash boxes. Our ash generation is 0.68% and dross generation is 0.39% of total production. Gross zinc consumption is 4.5%.
Please advise on quality of pre flux bath that should be maintained and method of zinc recovery from ash skimmings.

MADHU RANJAN
- Bhiwadi, Rajasthan, India


May 4, 2012

A. Sir,

If these are heavy angles (thick) then your results are average to good. If they are light (thin) angles then your results are very good to excellent.

I believe I have already responded on this website to your other questions.

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota


Ash gets stuck inside tubes

May 8, 2012

Q. We are galvanizers of tubular towers in which tubes are heated and pressed with a gap of 19 mm. While galvanizing these tubes, ash gets stuck to the walls of the tubes inside and these tubes are rejected.

Can you please guide as to how exactly to overcome this problem?

For your info, all the tubes are almost taken out of zinc bath @ 45 deg angle.

We are using triple salt of zinc amm. chloride with 18 to 22 Be and temp of flux is around 40° C and dried at 50° C

Shall wait for your suggestion.

Thanks & regards
Srinivasan.R

Srinivasan R
- Chennai, Tamilnadu, India


May 12, 2012

A. S.R.

Perhaps you could e-mail a photo of a "passing" and a "rejected" "TUBE" with some scale indicator (ruler or tape measure or a human hand in the photo). I have had very good success in reducing ash on product over the years via flux composition. In the last 1.6 years I have had outstanding success, via other means of eliminating flux and ash sticking to the product. The work goes on.

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota

June 11, 2012

Q. Dear Dr.Cook,
Refer to my question dated May 8th & your reply on May 12, thank you very much for replying. Sorry being late as I was on my holiday.

I attach 5 photos which indicate ash sticking to the walls of the tube inside.

(Click thumbnail graphic for higher resolution photo)
43365-1thumb  43365-2thumb  43365-3thumb  43365-4thumb  43365-5thumb

I would be very thankful to you if you can help us out on this issue.

It is considered rejection by the client.

Hoping to hear from you.
Thanks & regards

srinivasan.r [returning]
- puducherry, India


June 18, 2012

A. SR
I am not able to determine your problems from your photos.

Crux Dee
First I do not necessarily believe the flux test results. Secondly you are using mixed (both USA and European methods). Your have high temperature 65 °C. (USA) but high Baume' and low ACN (Europe) flux. My experience is that such mixing of methods does not work properly. I do not have a "manual for flux preparation."

M.Patel
What is the chemical composition of the brass wire and why would you want to galvanize brass wire?

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota


May 9, 2012

Q. HOW TO PREPARE THE HOT DIP GALVANIZING FLUX SOLUTION

REGARDS
NAG
CHEMIST

NAGESWARA RAO CHINTA
- HYDERABAD, INDIA


May 9, 2012

A. Hi, Nag.

Sorry, but in this context I can't quite understand the question. Please take a paragraph or more to try to phrase your question in terms of the answers that are already on the page. Thanks!

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


May 17, 2012

Q. Hello Sir,
Recently I sent my flux sample for a detailed chemical analysis and what I got the results is following. As we are new in hot dip galvanizing and have not reached the profit path, will someone kindly suggest prime actions to control the process fairly as our ash/dross limit is high and I heard that it's because of a bad flux. Test Result Says,
Zinc, Total = 108 g/l (gram per liter)
Ammonium Ion = 59.5 g/l
Zinc Chloride = 225 g/l
Ammonium Chloride = 172 g/l
pH at 25 °C = 3.92
Density at 25 °C = 1.2057 g/l
Total iron = 1.19 g/l
Baume at 25 degree C = 25
While we are maintaining our Flux Bath temperature at a value above than 65 degree C.
Zinc bath has,
Zn= 98.8
Iron=0.02
Lead=1.09
Copper=less than 0.01
Aluminium = less than 0.01
Mn= less than 0.01
What's your expert advise?
Thanks!

Crux Dee
- Dammam, KSA

First of two simultaneous responses -- May 17, 2012

A. In your zinc analysis you said "less than 0.01%", did you mean less than 0.001% ?

Geoff Crowley Geoff Crowley
galvanizing &
   powder coating shop
Glasgow, Scotland

Second of two simultaneous responses -- May 18, 2012

A. Sir:

Obviously you are using a European flux composition, which in my experience does not provide proper fluxing and economical results. It is true that I could calculate how to convert this flux to the North American flux formulation and in a detailed way. Actually that would be a mistake because I do not even trust the test results given. However, if this were done properly and you were trained to maintain good flux then you would have perhaps one item under control and you would then have only perhaps nine more items that need to be worked on to get good results.

My article TESTING AND CONTROL OF HOT DIP GALVANIZING FLUX in the journal METAL FINISHING would be quite useful and likely can be purchased on the internet or obtained via inter-library loan.

I do not understand why Europeans think their flux formulation is a good one? Flux manufacturers in the USA have been angry with me for nearly 40 years because the quantity of flux used in the USA is much, much less than before I started working in galvanizing. The use of flux in the USA is also much, much less than in Europe.

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota

May 19, 2012

Q. Sir Geoff Crowley,
Yes its %. Sorry I forgot to mention that.
And Dr. Cook,
Was that flux description for me? And I really want to obtain your manual for flux preparation.

Crux Dee
- Dammam KSA


May 20, 2012

Q. We are performing the process of hot dip galvanizing for coating on the brass wire with the diameter of 3mm.
In this we are facing a problem of improper bonding lets say like after few months the coating will peel-off from unspecific area. We are not able to find the proper flaw in our process can you give us your valuable suggestion so that we can go for production stage trial?

Best Regards

M.Patel
- Dubai, UAE


June 21, 2012

Q. At what Fe+2 concentration does one have to consider ACNV as opposed to just ACN?

Kevin Carroll
- Long Beach, California


June 22, 2012

A. Kevin:

Good question. A few years ago I gave a corporate workshop and I tested the 10 fluxes first. In one case, the ACNV was about 0.4 whereas the ACN was 1.2 (near triple salt). The reason for such deviation was obviously the high iron content, which by my limited memory was around 5%. The easy way to answer this question is to calculate both ACN and ACNV but ALWAYS use ACNV as your standard. It has taken many years just to get galvanizers knowledgeable to ACN. Now the task is to get them to understand and use ACNV.

As a side note, a few months ago I found an ACNV of 1.0 for a 10,000 gallon flux tank and advised that about 4,500 pounds of ammonium chloride was required to attain quadraflux with ACNV of 1.6. The galvanizer added about 3,000 pounds of ammonium chloride and then sent it to a flux company for testing. The result was 0.69 for ACN which was clearly NOT correct. This flux had a sulfate of 1.2% and iron (Fe+2) of 0.8%. I have never really decided where to include sulfate but I expect it should be included in the denominator. This has not been an issue for me because the way I test gives ACNV directly and I have used this ACNV very successfully for many years. 15 years ago I made up in lab a flux with ACN = 1.00 and sent it to 13 labs. ALL the labs got VERY WRONG RESULTS. The results are published in METAL FINISHING under a title like TESTING AND CONTROL OF HOT DIP GALVANIZING FLUX.

Dr. Thomas H. Cook
- Hot Springs, South Dakota

June 25, 2012

Q. Dear Dr. Cook.

The composition of the Brass wire is 60% copper and 39-39.5% zinc; balance is impurities.

The need for galvanizing the brass wire is for a marine application.

Please suggest what kind of flux can be used for the same, and whether we can use Zinc Ammonium Chloride or if anything else is required for the base metal brass?

Best Regards

M.Patel
- Dubai


June 25, 2012

A. Sir,

I expect triple flux will allow you to galvanize brass wire. Over time, copper will enter the kettle zinc and likely cause the iron zinc kettle to have a short lifetime.

I have no experience in galvanizing brass.

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota

July 11, 2012

Q. Dear Dr Cook.
We have a continuous steel wire galvanizing line here in Kampala,Uganda.We are facing the following problems:
High dross formation and An acid flux bath.
We try to neutralize the flux bath by adding an ammonium solution but the rate of con termination is high.
Yes we have a rinse tank but still its not enough!
Sir, what is your expert advise on the above?

Collins Wasswa
- Kampala,Uganda

----
Ed. note: Thanks for addressing Dr. Cook with respect, Collins -- and sorry to be a stickler, readers ...
But for legal reasons we must continue to restate the fact that, while you may get general hints and guidance from knowledgable people in this forum, you only get "expert advice" by specifically retaining a consultant to do an on-site study of all aspects of your situation :-)


July 18, 2012

A. Collins:

Are you "wet" or "dry" kettle? What is too high of rate of dross? How long do your kettles last?

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota

September 23, 2012

Q. Dear Dr. Cook:
I have a serious problem with bare spot because of Chinese raw material. I produce steel tower angle and plate, our flux is double salt acn 0.8 and fe+2, 0.28%, so, my supervisor tries to solve the bare spot problem by brushing the angles with ammonium chloride solution for 45 minutes, then immersing in zinc kettle. The result became okay but as per my little experience the dross will increase too much. I read an article before that every additional gm of ammonium chloride causes 20 gm of dross, is it right or not? And what's the side effects of doing it my supervisor's way?
Thanks.
Regards,

Ahmed Hassan
technical manager - Yingkou Anshan China


First of two simultaneous responses -- September 25, 2012

A. Sir:

Your English is excellent.

It is NOT true that 1 gram of ammonium chloride in the flux gives 20 grams of dross at the kettle.

Your question reminds me of my work 40 years ago and for this I feel badly for you. Properly formulated, tested, and used, quadraflux does an excellent and extremely effective job of galvanizing your types of steel (assuming the pickling is good). Unfortunately there are some extremely bad inhibitors in the market place that prevents proper pickling. I do have a good article in the journal titled Metal Finishing. The name of this article is something like: "Testing, Control, and Use of Hot Dip Galvanizing Flux." I looked for a copy here at home and was not able to find it to properly reference it, sorry. This website has a search engine and I have made many replies to questions like yours. So please search this website and the general web via Google.

Regards, Dr. Thomas H. Cook, Hot Springs, South Dakota, USA

Dr. Thomas H. Cook
- Hot Springs, South Dakota

Second of two simultaneous responses -- September 25, 2012

A. Dear Ahmed;

Is your kettle dry or wet? In dry applications, excess ammonium chloride will have no effect, just extra fumes.

Why don't you try using sandblasting -- would be quicker and cheaper.

Ozge SARACOGLU
- Ankara, TURKEY


September 26, 2012

Q. Hi Ozge,
Sorry, I forget to tell you that our kettle is dry and we have preflux double salt with temperature 50 °C and in our kettle we never use lead; we can use nickel and aluminum and bismuth alloys.
And I have good friends in Turkey, Mrs. Isik Spaci. They are good galvanizing consultant.
Thanks
Regards
Bye

Ahmed Hassan
- Liaoning, China


September 26, 2012

Q. Dear Dr. Cook /Mr. Ozge.
Thanks a lot for your kind support.
1st, I suggested the shot grit blasting since the sand blasting will increase the silica in the degreasing and pickling.
Regarding the ammonium chloride, does it really only cause white fumes, or increase the dross & ash also?
Also, I think that one mole or gram from iron gives you 25 mole or grams. Am I right?
Dr. Cook, you kindly suggested me to use quadraflux, can you give me the best specifications (composition ratios, pH, temperature, etc.] Please advise.

Thanx
Regards

Ahmed Hassan
- Liaoning, China


First of two simultaneous responses -- September 27, 2012

A. Sir:

Quadraflux is 1.6 parts ammonium chloride and 1 part zinc chloride. Best baume' is 13. Best pH is 4.2. Best temperature of flux solution is 71 °C. Keep product in flux solution about 3 to 5 minutes to heat fully the steel. Take out steel and lay at an angle to promote drainage. Drying should be done within a few minutes. Fluxed steel should enter kettle with little spatter. Faster entry is best. Slower withdrawal is usually best.

Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA


Second of two simultaneous responses -- September 28, 2012

A. Dear Ahmed;

I will give Mrs. Sapci your compliments at our next meeting.

Ammonium chloride will cause increase in white fuming. Double salts are always "fumeless" but as triple (ZnCl2.3NH4Cl) or quadraflux (ZnCl2.4NH4Cl) would have higher fuming. You might also try to sprinkle ammonium chloride powder before you dip into zinc. This is very old application, causes heavy fuming but best option for poor pickled parts. It won't affect your dross and ash formation, but will cause drop in aluminum content (especially if your kettle is small).

Also you might try to agitate your acids strongly or heat them over 35 degrees. This would give better pickling.

One more option; dip your products by normal procedure, immerse, withdraw, dip into flux again without cooling, re-galvanize. I used to do it a lot with angles, I-U beams, which have very poor steel quality. But of course coating thickness will exceed 150 microns.

Dross is 96% zinc and 4% iron. Thus we can say 1 gram of iron will produce 25 gram of dross. But actually this doesn't mean that every 1 gram of excess iron will result in that much dross. Some will dissolve in zinc (if your nickel is high this solubility will be less) some will oxidize while immersing, (zinc ash may have 3% iron) etc. The rest will form dross.

Quadraflux is ZnCl2.4NH4Cl. Best ideal pH range is 4-4.5 (best will be 4.2) - use titration method, pH meters are rubbish -- and ideal Temperature would be 60-65 degrees.

Ozge SARACOGLU
- Ankara, TURKEY


September 29, 2012

A. Ozge:

35 °C (95 ° F) is too hot to heat 17% HCl. The fumes will destroy the roof and the building, which will happen anyway if a good inhibitor at the right concentration is not used.

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota

October 2, 2012

A. Dear Mr. Cook;

Of course I am assuming inhibitor, good ventilation system and moreover an enclosed pretreatment unit. Thanks for mentioning about all these.

Ozge SARACOGLU
galvanizer - Ankara, TURKEY


October 2, 2012

A. Sir:

HCl is a gas which is heavier than air. It fills a galvanizing plant from the floor upward. This gas along with water vapor is terribly corrosive. I have seen steel corrosion in warmer climates for areas around a galvanizing plant corrode to orange black dust over the years. The best HCl fume control that I saw exhausts the HCl gas down through the floor. Simply put the best HCl temperature range in my experiences is between 70 and 85 °F. Above 85 °F the workers and the cranes suffer.

From which country do you purchase your HCl inhibitor and at what concentration do you use it? Also do you test its effectiveness in the HCl pickle tank?

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota

First of two simultaneous responses -- October 4, 2012

A. Dear Dr. Cook;

I know all these. Because of all things you mentioned, we have good ventilation system that is sucking and blowing air 10 cm below the acid bath top edge. Thus, all acid fumes are sucked and sent to treatment unit. I guess it is forbidden to give brand name but we use an Italian famous brand, which has 2 additives (inhibitor and anti vapor). Also our environmental advisors regularly measure the acidity in the air and reports that it is very low. And also you can notice little smell, even standing in front of a fresh acid.

Even I don't usually exceed 30 °C (guess it is like 85 °F) , but in extreme cases exceeding this value does not cause problems for us.

Ozge SARACOGLU
galvanizing - Ankara, TURKEY


Second of two simultaneous responses -- October 4, 2012

A. There's a lot to be said about having a good inhibitor, as Tom has said.
There are some that prevent proper pickling.
There are some that do nothing useful.
There are only a few that do what you really want them to do - allow the dissolving of oxides of iron while preventing dissolving steel.

HCl fume is an issue, dependent of temp and concentration.
In "sunny" Scotland the temperature is not much of a problem. I remember one year breaking the ice on the surface of one pickle tank!

Geoff Crowley Geoff Crowley
galvanizing &
   powder coating shop
Glasgow, Scotland

October 5, 2012

Q. Dear Geoff;

Do you mind if I ask about your average pickling time during "winter" (for fresh acid and for 30 baumé)?

Ozge SARACOGLU
galvanizer - Ankara, TURKEY


October 6, 2012

A. Ozge,

You answered my question of where you get your inhibitor EXACTLY AS I EXPECTED. Regarding this supplier I respond "NO COMMENT."

Incidentally 30 °baume' FRESH HCl is NOT available, the highest concentration is 20 ° baumé (e.g. about 35.5% HCl). After being fresh the dissolving of iron and zinc causes the baum é to rise to the 30 to 40 ° baum é range. Some iron is required for good pickling in HCl.

In my inhibitor testing of 38 years ago (now published in the magazine METAL FINISHING) I did all my testing at 3 parts inhibitor/10,000 parts mixed acid (e.g. 3 liters inhibitor/10,000 liters mixed acid). For sulfuric acid I used 10% acid, 2% iron, 1% zinc and 160 °F. Only one inhibitor (produced in the USA) did everything I wanted, including NOT slowing the pickling (in a separate test). For HCl I used 1:1 HCl/water 3/10,000 and the same iron and zinc and at 90 °F. Again only one (produced in the USA) did what I wanted.

About 10 years ago I was called into a new start-up plant using sulfuric acid, which previous to my arrival had 3 (55 gallon) barrels of fume suppressant plus inhibitor put into each of three 20,000 gallon pickle tanks. The fumes were so bad that I could NOT walk across the plant floor crosswise. Simply put, my lungs closed up and I could not take a breath. The workers were having nose bleeds and quitting. I drove to a nearby galvanizer and obtained two 5 gallon buckets of the good inhibitor and put one gallon into each acid tank. The next morning I came into the plant and the workers all came up to me and were thanking me for the clean air that they could take a breath. The supplier blamed the first product on a "bad batch." RIGHT!!! With the good inhibitor the air in the plant was the same as clean outdoor air.

A few months ago I went to the East Coast of the USA and noted that the HCl was not properly pickling. A test confirmed that the acids were over-inhibited (same supplier) as the case 10 years ago. This was quite unusual because the plant manager said they had not added any inhibitor for the last 5 months. To increase pickling they had heated up the HCl tanks and the guy was there getting ready to remove and replace the roof. All the acid tanks were then hauled away and new acid brought in and inhibited with the good inhibitor. It was a pleasure having acid that pickled very well and with almost NO fumes. Thus the combination of a good inhibitor and with proper testing, fast pickling, very low fumes, and very long acid tank lifetimes are easy to attain.
Geoff has very good experience.

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota

First of three simultaneous letters -- October 9, 2012

A. Pickle time?
It's like asking how long is a piece of string.
There are so many variables.

But, structural steel, (beams and columns for buildings) in winter might take 2-4 hours.
We manage to use pickle tanks where heavy long pickle time material is at the bottom, while lighter quicker material sits near the top.
In another plant further south (warmer), winter pickle time can be 1-2 hours for light material.

Geoff Crowley Geoff Crowley
galvanizing &
   powder coating shop
Glasgow, Scotland

Second of three simultaneous letters -- October 9, 2012

thumbsup2Dear Dr. Cook,

Sorry for my rubbish English, I have asked for 2 different values; new fresh acid and 30 Baume acid (after it is used and reached to 30 Baume).

After your good response I will consider about the inhibitor and temperature. Thanks for your help.

Ozge SARACOGLU
- Ankara, TURKEY


Third of three simultaneous letters -- October 9, 2012

Q. Dear Sirs:
I am really enjoying with such technical discussion, I really feel proud to be involved. Regarding my conditions --
Our acid pickling concentration always was kept between 8.0 up to 12.0 to avoid acid fumes; we have same acid suction unit as explained by our friend Ozge but from a Chinese supplier.
Regarding the inhibitors, I am a little bit worried since we are using Chinese brand and I can't trust it. It may be causing poor pickling. I hope that Dr. Tom can recommend a good brand for us from local market (China) if available. Otherwise, give us the way how to test it. Final solution we can import from international market as per his suggestion.
Thanks
Regards
Rashad

Ahmed Rashad
- Liaoning, China

----
Ed. note: Thanks, Rashad, proud to know you. We wish we could be all things to all people, but we have learned from decades on line and tens of thousands of threads that we simply can't recommend particular brands or suppliers in a public forum. It leads to the raucous hostility that has destroyed so many forums; it leads to race-to-the-bottom spam with shills posting with fictitious names posing as satisfied users (and even masquerading as other people); and it makes it impossible to retain advertisers to keep the forum going. The best way to preserve a forum that offers camaraderie and impartial technical answers seems to be to work towards removing all commercial benefit from the postings, even when that means an answer isn't wholly satisfactory, and keep advertising a separate issue. Sorry. We spend many hours editing or discarding hundreds of pieces of spam submitted as answers for posting on this forum every week.


October 10, 2012

A. Ozge:

30 some years ago I found a wetting agent for flux that I liked. I used vacuum (water aspirated) and reduced the volume of this wetting agent by 95%. I then added water back and got the same good results as a wetting agent. I contacted the maker of this wetting agent and indeed he admitted that he took 2 gallons of the concentrated wetting agent and then added 50 gallons of water to it and sold it by the barrel at about $2,000/barrel. I chose NOT to deal with this guy who liked to dilute a good material and sell it for a huge profit. Later I found a concentrated material that works extremely well at 1 to 3 parts/10,000 parts of tank volume. (e.g. 0.01% to 0.03%). Thus from this posting you should note and understand that if an inhibitor company recommends much higher concentrations it is likely the inhibitor is not very effective or watered down. Also realize that the more inhibitor an inhibitor company sells the more money the inhibitor company makes. Also some inhibitor makers do not disclose on MSDS sheets what is in their products which should make you question why not? In the USA disclosure on MSDS sheets is a requirement of law. An acid inhibitor MUST nearly prevent additional attack of the bare steel after the mil scale is removed, and it MUST NOT slow down pickling (removal of mil scale). Thus two types of testing are required: 1)acid attack on steel in a stressed condition and 2)pickling speed tests on steel with a mill scale coating. Less fumes in the plant come automatically with a good inhibitor. There are fume control agents (which are NOT inhibitors) as well but I rarely use them except in special cases.

My article in the magazine METAL FINISHING about inhibitors is titled something like: "Testing and Use of Acid Inhibitors." From this article you can test and evaluate inhibitors to find the one or two (from many) that suits your needs.

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota

November 15, 2012appended

Q. I am an employee at one of the construction companies that manufacture scaffolding and formwork.
Most of our products are galvanized, therefore we set up a galvanizing process. It's been running 75%, but I am still confused as to the determination of the proper usage of fluxing solution because I'm new in this issue. Whether mono salt, salt double, triple or quad salt?
I need help to determine which fluxing solution I will use in my company now.

Defi Afriyanti
- Cikupa, Tangerang, Indonesia


November 17, 2012appended

Q. How do you purify triple salt flux which is contaminated by hydrochloric acid? Test procedure to determine the iron content in a flux solution?

Psalm Velarde
production - Dubai, UEA


February 3, 2013 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Dear Sir,

Please give me details of flux (% ammonium chloride, zinc chloride, & other )

Thanks & regards

SAGAR NAIKWADE
- Pune, India


February 17, 2013

Q. Hi sir

I am responsible of qc in galvanizing factory. I have an article about flux. Please guide me what should I do?

Best regards

meysam karimi
responsible of qc - iran-khorasan-mashhad



February 20, 2013

Q. Dear sirs,

I've just started working in a company that galvanizes steels for power transmission towers. The problem is, it doesn't have any knowledge about the chemical of the process and I'm in this field only for 5 months. We're making some tests to prove what is good for us and what is not, but we're still facing some difficulties

One of the problems we have is about the preflux additives, we've just prepared a new preflux bath because the old one had 50 g/L of iron contamination. Some suppliers told us about some additives and I'd like to know if they really work or are just people trying to sell their products. The additives are:

-Additive for complexing of iron: a product that maintains the iron concentration low by complexing the iron contamination;
-Additive containing nickel: some said that nickel in the preflux bath help the homogeneity of the zinc layer, but others say that this nickel only oxidizes in the heating before the zinc kettle, forming ashes;
-Additive to make the steel more wettable.

These additives really work? Is there another kind of additives I can use in the preflux bath?

Regards,

Daniel Athayde
Chemical Engineer - Belo Horizonte, Brazil


simultaneous February 23, 2013

A. See some people even add acid to the flux but they tend to miss it that this would go to the GI tank.Better way is to change the water after pickling on a regular basis and check the iron content of it.If the water after pickling is clean you wont see iron content in your flux increasing.Changing of Flux is an Expensive part but changing of water after pickling is relatively cheaper;)

nitesh agarwal
- mumbai, India


February 23, 2013

A. Daniel,

Regarding additives for flux:

There is no additive to complex iron in flux.

Nickel in the flux is toxic, according to the USA CDC, nickel in any form causes lung cancer. Also nickel in the zinc at 0.05% only works for silicon semi-killed steel (e.g. 0.05% silicon to about 0.15% silicon). In the USA nearly all steels are fully-killed steels, silicon above 0.15% or aluminum above 0.03% aluminum. For these steels nickel is of little or no value.

There is an excellent surfactant in the market which at 0.03% reduces the surface tension from about 80 dynes/cm down to about 30 dynes/cm. It also is an excellent corrosion protector for steel and by having a 1 inch layer of suds on the flux solution reduces the heating cost for the flux tank by 50%. This wetting agent is made in the USA and Germany.

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota

Best ACN for my case

July 8, 2013

Q. Dear sirs,

My company sent the flux samples of different suppliers to a lab. The two samples had different ACNs and I still don't know which one is the best for my case.

We galvanize about 80% angle steel and the other 20% are sheets. We are not able to heat the preflux more than 40 °C, but we have an oven.

What is the best for me? An ACN of about 0.4 (MONOSALT) or is there another good composition for my case? I've read that the best for sheet is the monosalt, why is this? Is it because of the low ammonium concentration?

Thanks!

Daniel Athayde
Chemical Engineer - Belo Horizonte, Brazil
  ^- Privately contact this inquirer -^


July 29, 2013

Q. Dear.Dr.Cook,
I run plating business in South Korea.
I read your posting on finishing.com and I would like to ask some questions, if you don't mind.

1. In your posting, there's a direction that 'Add some wetting agent during fluxing process'. So I added made-in-Korea wetting agent over 2%, but only resulting 40 dyne/cm of surface tension.

2. Is it ok to get less zinc consumption, less ash and less bottom dross effect with surface tension 40 or so?

3. I would like to know correlation between zinc consumption and surface tension.

4. And, is there any negative effect in flux cistern, pouring some addition agent of 2% - 4% of total amount?

Kwak Dong Bin
- Ulsan, Daun-Dong, South Korea
  ^- Privately contact this inquirer -^


July 30, 2013

A. Sir:

There is no way I can answer your questions because I have no idea what your wetting agent is. I do not know if it would be beneficial or bad.

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota


At what point does recirculating waste water ruin the flux?

December 27, 2013

Q. Dear Dr Cook and other readers,


I am working as a chemist in an HDG plant.
My question considers the effect of washing water on flux. We are using HCl for pickling. As we don't have canalization, waste water for rinsing has to be sent to authorized companies and thus we were forced to deal with this problem in a way that our waste water is circulating. It goes from washing tub in to neutralizer (NaCl is added) and it is neutralized at 8,1 pH; some coagulants and flocculants are added for precipitation and after that water goes to precipitation tank where the sludge is pulled out. "Clean" water goes back in the wash tub and it is used again.
The only problem now is that the water currently contains 83% of NaCl (100% corresponds to 36 g/l), total dissolved solids are 19 g/l, conductivity is 36mS at the temperature of 13,2 °C.

I am aware that at some point we will contaminate flux with Na+ ions. Do you know what other problems I can expect? What can I expect in the dipping process, more smoke, ungalvanized areas?
We are using our type of flux for 8 years now where the ratio of ZnCl2:NH4Cl is 2:1, flux is 21 Baume, temperature 25-35 °C, content of Fe2+ lower than 1 g/l, and we don't have any problems in production -- black spots are really rare.

Does anyone else have the same experience with rinsing of goods in salted water? At what level/concentration of NaCl /conductivity do you send it out? At what concentration of salt can I expect that the material after rinsing and before fluxing, although it takes few seconds, will start to corrode? Is it possible that material goods will corrode after fluxing? Do you have any suggestions for me?

Really looking forward to your answer.

Vedrana Bukal
- Zagreb, Croatia
  ^- Privately contact this inquirer -^


December 27, 2013

Q. Dear Sir,

Currently we are buying flux from a local supplier. It's giving us a lot of problems. When i ask the supplier whether it's:

1)Monosalt
or
2)Triple salt

He is unable to answer. According to him, this type flux is specially designed for my plant.

Specific gravity of neat solution of fresh flux is: 1.15
Temperature of flux is: 51 °C.
I am suspicious of the supplier because the quality of flux he is supplying us is causing us a lot of problems.

After dipping the product into flux solution, we will have corrosion line on the surface of the product and it creates a lot of ash during dipping in the zinc pot.

Thanks
Param

Jeet singh
galvanizing - Selangor ,Malaysia


January 12, 2014

A. Sirs:

In hot dip galvanizing fluxes certain non-volatile chemical compounds may be present (even in brand new fluxes). These may include calcium chloride (CaCl2), magnesium chloride (MgCl2), manganese chloride (MnCl2), sodium chloride (NaCl), and potassium chloride (KCl).

About 30 years ago I found 13% sodium chloride in a flux from Iceland and the galvanizer had 13% rejects. A reject being product that had to go through the kettle twice. When the flux was replaced with a flux having no sodium chloride the rejects went away. Same thing happened in Madrid except it was 20% sodium chloride in a pipes galvanizing plant with 20% rejects and again rejects disappeared when flux with no sodium chloride was put in the flux tank.

I now know that if the solid flux contains about 3% total non-volatiles (or about 8 grams/liter in the working flux), then the rejects will be about 5%.

I recommend that you have your working fluxes tested by icp/ms and post the results. The results should be in mg/liter of the chlorides of the various metals.

Vedrana-- You cannot neutralize with sodium chloride (NaCl), you must mean sodium hydroxide (NaOH). The proper pH of rinse before flux is 5 or lower, otherwise the product will corrode before you can get to the zinc kettle. Your current procedure is bad and you will contaminate the flux.

Jeet-- Have your incoming (new) flux tested and post the results.

Regards, Dr. Thomas H. Cook, Hot Springs, South Dakota, USA

Dr. Thomas H. Cook
- Hot Springs, South Dakota


May 12, 2014

Q. Dear Dr. Thomas.
Which flux salt (mono, double, triple, quadra) you recommend me to use in my batch galvanizing plant since my dryer is not really effective. Also what can I add to my flux tank to stop the zinc spattering or scattering from my kettle since my dryer is not effective as I told before.
Thanks,
Regards,
Rashad

rashad ahmed
hot dip galvanizing - borjal arab , Alexandria , egypt


May 13, 2014

A. If you would like to try a flux extremely low in non volatile salts I suggest you try PREACT. We manufacture our flux at our plant in Freeport, TX USA from virgin raw materials to insure the lowest possible level of non-volatile salts.

Thorn Baccich, President
Mineral Research and Development - Harrisburg, North Carolina USA


May 2014

thumbsup2Thanks for your participation Thorn! We don't recommend one proprietary product over another in this forum, nor can we ask our supporting advertisers who make the forum possible to bear the costs of postings that steer the potential customers to non-advertisers, so we had to abbreviate your posting a bit.

But you are implying that low-volatiles in flux is an important issue, and it sounds to me like a valid technical point. I don't know enough about galvanizing to argue the point either way, but I am intrigued with why this might be considered important, and I invite you to expound on the technical issue if you would. Thanks!

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

May 15, 2014

A. Ted, I can appreciate your comments. The best expert to ask regarding the problems of high levels of non-volatile salts in a galvanizing flux can cause is Dr. Thomas Cook. He has done a great deal of work testing fluxes. He is by far the best expert I know on this topic.

Regards,

Thorn Baccich, , President [returning]
Mineral Research and Development - Harrisburg, North Carolina USA


May 2014

Hi again. No question about Dr. Cook's expertise, which has been demonstrated many times on this site, let alone other places. However, unless someone tells us that there are several suppliers of fluxes with low non-volatiles, the topic would become a public discussion of one proprietary product -- which is always a disaster for a dozen reasons :-) Thanks.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

May 15, 2014

A. Dear Mr. Rashad Ahmed;

Generally double salt flux is used among batch galvanizers. However you can use higher ammonium chloride content but it will cause excessive fume.

If you don't have a dryer you can:

1- Heat up your flux to 60 °C with a simple boiler and heat exchanger coils
2- Use flux surfactants (will be cheap and easy to use)
3- Soprin has an flux additive for exactly that purpose

But please keep in mind that nothing will be as advantageous as a good drying system.

Ozge Saracoglu
- Doha, Qatar


May 16, 2014

Q. Hi friends,
Mr. Ozge. Thanks for your existing reply and I appreciate your help a lot. Regarding fumes, no problem; we have our effective fume suction unit.
So what is the best flux to give us best quality and consumption?
As well do you an idea about pickling accelerator?
By the way what do you do in Doha?
Thanks
Regards
Rashad

rashad ahmed [returning]
- egypt , cairo


May 22, 2014

A. Dear Mr. Rashad Ahmed;

For quality issue, actually I have never noticed any difference between double salt and triple salt. Moreover if you can eliminate fume, and I am assuming that your pickling is not perfect (as you want to accelerate your pickling) triple salt can give you a better solution. Although the consumptions are nearly the same, triple salt is cheaper than double.

I have seen a chemical supplier is offering pickling accelerators, but I have never used it or seen any plant using it. I am not sure chemical approach to accelerate pickling can efficiently work. Maybe Dr. Cook can explain that subject to us.

But, kinetic approach for accelerating works perfectly. You can heat up your acids to 30 °C, and give some agitation by a mixer or blowing air in. By applying both, you can double your pickling efficiency. But be careful not to exceed 30 °C much. It will cause excessive acidic gas extraction, and also it makes Dr. Cook so much angry :-)

I am currently installing a galvanizing plant (14.5 x 1.8 x 3 m kettle dimensions) and a fabrication unit (fully automated pole production line and road barrier line). Actually main equipment installation is finished; we are doing the auxiliary fabrications and waiting for governmental approvals.

Ozge Saracoglu
- Doha, Qatar



May 27, 2014

Q. To reduce the Fe from flux bath I put in H2O2 . how can I remove the foam that appears on the bath surface? Because in this foam is very much Fe and I want to get it away from the flux bath .
Best regards,

George Condurat, dipl.ing.
- Bucharest , Romania


June 1, 2014

A. Dear George,

Didn't you filter your flux after adjusting pH and adding peroxide?

Ozge SARACOGLU
- Doha Qatar


June 18, 2014

A. Dear Sir...
Better you do continuous flux filtering system which helps to remove Iron content from Flux bath.

Ilesh G Vyas
Gunatit Builders

Manjalpur, Vadodara, Gujarat



July 4, 2014

A. George,

The reason you got so much foam when you added H2O2 to the flux was that your pH is too low. You must also FIRST add aqua ammonia (ammonium hydroxide) to provide OH- groups for the Fe+3 that is formed to make Fe(OH)3. Without the ammonia, peroxide self destructs to oxygen (the foam) and water.

Regards,

Dr. Thomas H. Cook
- Hot Springs, South Dakota, USA



June 18, 2014

Q. Dear sir

I need the method to analyse flux solution (Hot dip galvanizing) for iron content. The method which I have is by using KMnO4 with pink end point.

My problem is the pink end point never comes while analysing flux. It's found the the solution turns greenish black which cannot assure the end point.

Please help and guide which method to be used for analysing iron in flux which can show clear endpoint.

Awaiting response soon.
Regards
Dharampal

Dharampal Singh Salooja
- Jeddah, KSA


July 3, 2014

A. Sir,
Best titrant for Fe+2 is potassium dichromate with sulfuric acid/phosphoric acid buffer and sodium diphenylamine sulfonate. End point is from light green to deep blue.
Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA


July 5, 2014

Q. Dear Dr. Thomas
Thanks for response regarding Fe+2 analysis.
Can you describe a complete method to analyse hot dip galvanizing flux for iron content using potassium dichromate?

Thanks awaiting reply

Dharampal Salooja [returning]
- Jeddah, saudi arabia


September 19, 2014

Dear Sirs,
for flux treatment (Fe reduction) we made lots of experiments and one of the results is that the amount of chemicals (both H2O2 and NH4OH) is reduced when first adjusting the pH value by adding NH4OH and the oxidate the Fe(II) to Fe(III) and with this, Fe(III)hydroxide precipitates. But it is highly advised to "stop" oxidation and precipitation when the pH value decreases <3. For lower pH values the floc becomes bad and the separation of Fe(III) hydroxide with chamber filter press is much more difficult. There is a De-Iron-Unit on the market which considers all these items and treats the flux in parallel to the HDG process

Dr. Frank Schmelz
- Recklinghausen, NRW, Germany

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