finishing.com -- The Home Page of the Finishing Industry
no_pop_no_spam
HomeFAQsBooksHelpWantedsForum letter 50564
Serious Education ... plus the most fun you can have in metal finishing.

Delayed Blistering in Alkaline Zinc Electroplating



A discussion started in 2005 & continuing through 2017 -- add your Q to bring it back to the Hot Topics page.

(2005)

Q. We are having problems with delayed blisters in our zinc plated parts. The process is a rack operation with alkaline zinc, zinc content is 14-16 gr/lt and 120-140 NaOH. Client requires 15 to 35 microns and because of part configuration it is very difficult to plate, in order to achieve at least 15 microns in the lowest area, some areas are very close to 30-35 microns. We experienced delayed blisters 5 days after plating. 100% of parts where adhesion checked according to ASTM, tape test and were approved. Almost all the blisters have "popped" and we can see a black area underneath, but some blisters are "unpopped". What does the black area mean? We believe the pre-plating process is very thorough, parts are very clean. Base metal is Steel, hardened and tempered to 16-17 Rc, we don't consider this a hardened metal because of the low Rc value.

Some parts showed pitting in the finish; can these pits later develop into blisters?

We added agitation to the bath to improve efficiency and to renovate solution close to the plated parts.

Can bubbles from the anode be the culprit? There is a lot of gassing while plating is done. Plating at 4-5 Volts, 2 amp/sq. dm approx. for 60-70 minutes

Thank you for your help

Dargmar Jimenez
plating shop - Mexico


(2005)

A. The problem could be excess brightener in the bath.

Anil Ramesh Barsani
- Mumbai, Maharastra, India



Zinc Plating
by Geduld

November 21, 2008

Q. Yesterday my shop ran a bar through our alkaline zinc-iron electroplater line. It is a part we have run hundreds of times with little problems. Today I got to work and discovered that the parts had blistered post-production. This is the first time I have encountered this problem. I am not sure what caused this to occur. Stresses in the plating was my first thought but I don't know what could cause this. The part ran through trivalent black chromate after being plated. We have a new black on our line so I'm not sure if this could be part of the problem but I doubt it. Any insight into this problem would be appreciated. Thank you.

-Steve

Steve Humphries
Plating Shop Chemist - Grand Rapids, Michigan US


simultaneous November 21, 2008(2005)

A. I doubt very much it's the chromate. Most often, this trouble is caused by organic contamination/too much brightener.

Try running a Hull panel and see if you can reproduce the problem. Carbon filtering the plating solution might remove the contaminant, if that is indeed the trouble.

dave wichern
Dave Wichern
Consultant - The Bronx, New York


November 22, 2008(2005)

A. Steve,

There are many causes for blistering in plating (general) and alkaline non cyanide zinc (specific). In general, substrate preparation and/or solution contamination (i.e., hex chrome, etc.) are to blame. Frequently, latent blistering of alkaline non cyanide zinc deposits have been caused by excessive brightener (or high total organics). Some manufacturers claim that their products will not cause blistering to occur because they are polymer materials. Although I too am a supplier, I am still skeptical of these claims.

In you case I would:

a. Check cleaning (solution strength, age, ability to remove oils, temperature, electrical connections/rectifier on electroclean, etc.)

b. Check rinsing. Lower temperature rinse water requires higher flows to be as effective (10 °F. rise in rinse temperature is the same as doubling the flow rate). When rinsing highly alkaline solutions (cleaners, zinc) low rinse temperatures will hamper rinsing.

c. Check strength and cleanliness of acid pickle.

d. Check chemistry of plating bath (zinc metal, hydroxide, carbonates). Correct as necessary. If possible test for metallic contamination.

e. Check temperature of plating bath. One must remember the difference between room temperature and ambient temperature. Low temperature can cause blistering.

f. If you can get blistering to occur on Hull Cell Panel, try carbon filtration to reduce total organics (including brightener). If this does not work and you cannot test for metallic contamination, dummy. If you determine that there is chrome contamination consult your vendor for the correct amount of sodium bisulfite (metabisulfite) they suggest as a reducer.

g. Call your vendor!

Gene Packman
process supplier - Great Neck, New York


November 24, 2008

A. Dear Mr.Steve,
Delayed blisters may be due to poor cleaning or brightener overloaded. Carbon treat the bath (250 gm/1000 lit bath). Check oil level in the cleaner. If it requires go for fresh makeup for cleaner.

p gurumoorthi
P. Gurumoorthi
    electroplating process chemicals
Chennai, Tamilnadu, India




To minimize searching and offer multiple viewpoints, we combined multiple threads into the dialog you're viewing. Please forgive any resultant repetition.



Alkaline Zinc Plating is blistering after two months

March 22, 2011

Electroplating Engineering Handbook

Q. DEAR ALL,

I'm Deepan. We currently face major blister issue, where the component is a plain sheet. The dimension of the component 300 mm length * 50 mm width & 3 mm thickness. The component is "s" shape. We are doing alkaline zinc plating; the variation in the regular plating is 1:2 where the component is fixed vertically;

In the month of December this material was plated, Major reason for blisters are IMPROPER PRECLEANING AND IMBALANCE IN ADDITIVES.

If improper cleaning may be the reason, the blister would form within 4 - 5 days, so we are suspecting an imbalance in brightener-booster additives.

If the addition level of Bri- booster level ratio changes, what would happen?

Pls help me to find the exact root cause for this issue.

m_deepan
Deepan M
plater - Chennai, Tamilnadu, India


March 24, 2011

A. If they start as tiny blisters, I will guess that you are overcleaning/pickle of the steel, especially if it is a higher carbon steel.
If the blisters are larger, then it is normally under cleaning/ inadequate etch.
A thin oil film on the top of any of the tanks can also cause the problem.

James Watts
- Navarre, Florida


March 28, 2011

A. Hi,

There may be many reasons in electroplating with terms of blistering problem, but in case of Non cyanide alkaline zinc plating, the delayed blistering is common and as Mr. James stated that if your base material is of some carbon mixture it will cause a blister problem; but as you mentioned it's sheet metal, so this won't be a problem; I strongly recommend you to discuss with your supplier about the additives you use, mainly the brightener or as you term it booster. If this brightening agent is higher you may face such problem of blistering, so try it by changing it after you give a carbon treatment. You don't need to wait for the delayed blistering you can check by building up higher thickness for just testing it and heat and cool the component -- I mean thermocouple test.

I guess it would be of help.

Regards
Praveen

praveen kumar
Praveen Kumar
    plating process supplier
Mumbai, India



simultaneous April 9, 2011

Hi Mr.Praveen Kumar,

Thank for your valuable Suggestion,

You have mentioned about the excess brightener or booster ... If the brightener level is low & the booster level is moderate what would happen?

Is there any other testing method for finding out the proportion of additives?

m_deepan
Deepan M
plater - Chennai, Tamilnadu, India


April 10, 2011

Too much secondary brightener and too little base brightener

Sara


 
Sara Michaeli
chemical process supplier
Tel-Aviv, Israel



April 26, 2011

A. Hi,

Oh yes, you can follow Ms Sara's advice with regards to the brightener/Booster, but anyway check the cleaning system in your line -- it's also very important factor for Non cyanide alkaline zinc plating., I am sure you have anodic cleaning, and also don't pass on too much of voltage, let it be within your recommended limit.

praveen kumar
Praveen Kumar
    plating process supplier
Mumbai, India



May 17, 2011

A. Testing by hot water quench will help you in identifying the problem in your end soon. You can try a few parts a day after plating. If it fails, it's organics issue.

S.V. Aurobind
plating process supplier - Bangalore, India


June 30, 2011

Q. Dear Mr.S.V. Aurobind,

This hot water quench I heard it before, can you please explain briefly how this could helps, sir.

m_deepan
Deepan M
plater - Chennai, Tamilnadu, India



To minimize searching and offer multiple viewpoints, we combined multiple threads into the dialog you're viewing. Please forgive any resultant repetition.



May 7, 2013

Q. The blisters are observed not on the complete surface but on particular areas that is different part to part. Is the problem of blisters due to organic contamination behaving in the same or will it occur all over surface of component?

Sharma Narinder Kumar
- Ludhiana, Punjab, India


ASM Metal Handbook
9th Edition, Vol. 5
Surface Cleaning, Finishing & Coating

May 10, 2013

A. Dear Sharma: In our company we run alkaline zinc plating on a daily basis; once in a while we have a delayed blistering problem. 95% of the time is due to:
A)The acid pickle getting weak, because of use.
B) Too much brightener in the bath.

To correct the problem,
A) Analyse and change your acid, if needed.
B) If you determined (using Hull Cell) that you have too much brightener in your bath, put steel panels in your tank and dummy it out 2 to 4 hours at 20 to 30 ASF.

I think this will help you. Good luck.

Nick Cordero
plating specialist - New York, New York


May 20, 2013

A. Dear Sir,

The alkaline non-cyanide zinc plating is prone to delayed blistering. Organic additives are mandatory and bath cannot operate without them.The excessive accumulation of organic carbon in bath solution and consequently in deposit can result in blister formation.

Anodic alkaline cleaning prior to plating can help to some extent but additive chemistry is most important factor. Recently developed chemistry yielding more even almost equal LCD and High CD coverage/thickness has lesser tendency to blister. Highly bright deposits are likely to have blistering problems. Low exposure of substrate to mineral acids during pickling stage can help to minimize the blistering problem. Similarly higher carbonate level in bath beyond certain level reduces cathodic current efficiency adding further to blister forming tendency. In short the problem needs to be attacked from a number of angles.

Best of luck!

Dilip Thakur
- Mumbai, Maharshtra State, India


May 22, 2013

thumbs up signDear Nick Cordero /Dilip Thakur

Thanks for your valuable views. Definitely the problem occurred due to high organics from the brightener. After carbon pack and addition of ductilizer in spite of the brightener the problem is solved.

Sharma Narinder Kumar [returning]
- Ludhiana, Punjab, India



June 27, 2017

Q. We manufacture fasteners, and regularly sub-contract parts for zinc plating & yellow passivation to various British Standards.

We have recently had some parts rejected on us from our customer due to blistering & flaking, however we are confident that the parts did not leave us in this condition. This would suggest to me that we are experiencing the same delayed blistering as mentioned previously.

Due to our customers' demands, we have asked our platers to increase the time in the passivation stage in order to offer a brighter finish.

Is it likely that the blistering is caused by excessive time in this stage, or would it be that the concentration of the chemicals in the bath is incorrect?

Many Thanks,

James Adkin
- Chesterfield, Derbyshire, United Kingdom


July 13, 2017

Hi,
Too much organics in your zinc solution. Carbon treat it. That is a common problem with alkali zinc.

If not, the steel is heat treated before plating.
Regards

anders sundman
Anders Sundman
3rd Generation in Plating
Consultant - Arvika, Sweden


----
Ed. note: Peeling/blistering in alkaline zinc plating is a perennial problem. For more perspectives and experiences, readers may be interested in:
Letter 17233, "Alkaline Zinc Plating Delayed Blistering"
Letter 40868, "Zinc Plating with Trivalent Chromate is Blistering after Baking"

ADD a Q or A to THIS thread START a NEW THREADView This Week's HOT TOPICS

Disclaimer: It is not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices


©1995-2017 finishing.com     -    Privacy Policy
How Google uses data when you visit this site.