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topic 18375p2

How to measure Zinc plating & galvanizing thickness p.2 of 2



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A discussion started in 1998 but continuing through 2020

August 10, 2011

Q. I want to standardize my plating shop, so that I am working on SOP of plating. Now I stopped at yellow chromate (Zinc cyanide electroplating) station because here I have no standard for thickness/viscosity and I have no method for the measurement of same.

Your valuable and expert guidance will be highly appreciated

Abdul Baseer Siddiqui
Plating Shop Employee - Karachi, Pakistan



April 23, 2012 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Sir, I want to know which of these are the best method to measure plating thickness of Zinc Electroplating.
1. Destructive Type.
2. Non Destructive Type.
Also in Destructive which type is most accurate one.
Thanks & Regards

Kashi Sridhar
- Bangalore, India


April 25, 2012

A. Hi Kashi. We appended your inquiry to a similar thread which may help answer it.

Cross-sectioning is labor intensive and can be done poorly, but it is still the "referee" method that tells us what the "real" thickness is. X-ray fluorescence is very expensive but probably the most versatile and reliable non-destructive method. But let's not keep it dry as dust (and possibly misleading): tell us your situation :-)

Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha



January 16, 2013

Q. We use PosiPen for plating thickness testing which shows thickness 18 to 20 micron. But when the same sample is tested by x-ray testing, it gives only 6 to 8 micron. Why?

Muhammad Khan
- Karachi, Pakistan


January 16, 2013

A. Hi Muhammad. Both devices must be calibrated. You can use microscopic cross sectioning as the referee device if you cannot resolve the discrepancy. Good luck.

Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha


January 18, 2013

Q. Dear Sir,

Both are calibrated and also we have tested by Microscopic examination of a cross section but the Posipen result differs from both test whereas Microscopic examination and X-ray test result same. Also please mention factors on which Cyanide Zinc plating thickness depends.

Thanks

Muhammad Khan [returning]
- Karachi, Pakistan


February 1, 2013

A. Muhammed,
It seems to me you have your answer on the thickness discrepancies. Is it possible that there are other magnetic sources that are interfering with the PosiPen? It could be just a matter of technique using the PosiPen?

Main conditions that affect plating thicknesses are:
Current Density, time, metal concentration in the bath, bath temperature and pH comes into play most of the time.

Tim Hamlett
Tim Hamlett, CEF
aerospace metals distributor - Tamarac, Florida, USA


A. Hi again, Muhammad. You should also be tracking amp-hours and doing a Faraday's Law calculation of anticipated plating thickness. It may not give you the precise thickness but it is a great reasonableness check. Good luck.

Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha


February 1, 2013

A. I have done a lot of film thickness measurements over the years and have yet to find a method that will pass a measurement study (aka gauge reliability and repeatability study). Fortunately in my circumstance, measuring paint coating thickness, ways to evade this issue are available.

Ronald Zeeman
Coil coating - Brampton, Ontario, Canada


February 6, 2013

A. Hi Muhammad,

There a few things that can influence magnetic and eddy current type equipment for measuring thickness. Two of the commonest errors are to measure too close to an edge and to measure on a curved surface when the equipment has not been calibrated on a curved surface.

Brian Terry
Aerospace - Yeovil, Somerset, UK


February 11, 2013

A. Hi Muhammad,
I have just one line suggestion for you.
TRY DEMAGNETIZING YOUR PARTS before you use a POSI PEN.
All the best.

vikram dogra
Vikram Dogra
Irusha India - Chandigarh, India


February 12, 2013

thumbs up signThanks, Vikram. I'll bet you've given him the answer!

Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha



April 16, 2017 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. What are the thickness checking methods for Zinc Nickel electroplated components, other than XRF?

Rajendra Pawar
Jayvin Industries - Pune, Maharshtra, India


Digital version
mfg_online

(No longer published, but a copy is on Academia.edu)
Download it before it disappears.

April 2017

A. Hi Rajendra. For a discussion of the possible destructive & non-destructive thickness testing methods, please review the thickness testing chapter of the Metal Finishing Guidebook =>
which Ken Vlach suggested.

If you want suggestions for methods most appropriate for your particular application, please tell us your substrate material (magnetic/non-magnetic?, conductive/non-conductive?), the typical thickness (different methods have min. and max. thicknesses which they are appropriate for), and info about the parts and the area to be tested (do you want the minimum thickness on a pinhead sized area, or the average thickness on a flat shape).

Ken has offered the best general answer: try a magnetic gauge if the substrate is magnetic, the thickness is in the 5 to 25 micron range, you can't afford to destroy parts with destructive testing, reasonably sized flat areas will be tested, you want a simple inexpensive device, and a good statistical average thickness will suffice. Good luck!

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading



Removing chromate conversion from zinc for coulometric thickness test

October 25, 2017

Q. Hello all,
I would like to measure the coating thickness of electroplated zinc over mild steel by coulometry. The equipment manufacturer suggested to remove passivation before measurement. But I don't know how to remove the same. Please advise.

Vikas V S
- Cochin,Kerala, India


October 26, 2017

A. Hi Vikas!

I don't use coulometry, but removing passivation/conversion coating without removing zinc is really difficult.

I would put the part in caustic soda 10% until it de-colors and begins to make some bubbles (hydrogen). You rinse it and measure. This method will not remove much zinc and will indeed remove passivation from the plated part.

Regards,

Daniel Montanes
TEL - N FERRARIS - Canuelas, Buenos Aires, Argentina


October 31, 2017

A. Years ago (actually decades ago) when I ran the Kocour Drop Test I used to remove yellow chromates with an eraser. For clear chromates I used about the same time and pressure. And long before that, platers used to estimate the coating thickness by putting a plated part in a pickle tank and seeing how long it would take until it stopped generating hydrogen. The Kocour Test is just a more sophisticated version of that test.

tom_rochester
Tom Rochester
Plating Systems & Technologies, Inc.  
supporting advertiser
Jackson, Michigan, USA
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A. Tom's eraser method might not remove 100% of the chromate, I've never done an analysis, but it certainly removes the great majority of it quickly & easily while removing no zinc at all. If you must remove all of the chromate, maybe getting most of it off with an eraser before doing Daniel's method is the best approach?

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading



Testing Alkaline Zinc vs. Acid Zinc with Eddy Current

April 24, 2020 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. We have two types of plating lines at our facility: Acid-Chloride Zinc Electroplate lines and one large Alkaline Non-Cyanide Zinc Electroplate production line.

We utilize an eddy current device for measuring zinc thickness on the products plated. When we calibrate our device for measurements we use a conductivity factor of "2" to measure alkaline zinc plated product versus a conductivity factor of "1" for product plated on the acid lines.

I asked internally as to who made the assessment that a conductivity factor of "2" should be used to measure alkaline deposited zinc and I was told that it has to do with how zinc is "laid down" on the substrate that requires this; that being said they could not effectively explain why "2" was the chosen factor.

I don't know if I am being clear enough when I ask this question, but why would one use a conductivity factor of "2" for eddy current measurement of Alkaline deposited zinc instead of "1". Isn't zinc on steel just that...zinc on steel? Does it truly matter what type of plating bath is used in terms of how you measure the deposit?

I hope I am being clear enough for anyone who can help!

Cody Powell
Quality Systems Manager - Reedsburg, Wisconsin, USA


April 2020

A. Hi Cody. My knowledge of this is only book knowledge, not hands-on, but we appended your inquiry to a thread where Ken Vlach told us that the eddy current conductivity of the different zinc platings do differ (he refers you to the Metal Finishing Guidebook); since you are plating on a magnetic substrate, his advice that a magnetic gauge would probably be a better approach sounds on the money to me :-)

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading



Can I calibrate magnetic thickness gauge with a standard or must I strip a part?

May 23, 2020

Q. When measuring the thickness of zinc plating on steel using a magnetic induction gauge, can I calibrate zero on steel provided with gauge or do I need to attempt to remove zinc coating from a part to use as zero?

Bennett Bergquist
- Rupert, Idaho


May 25, 2020

A. A reference standard will give you a close approximation. But if you want to be more accurate use an unplated article for zeroing your instrument. Most platers keep a few unplated articles for this purpose. If those aren't available, you can strip the articles to obtain a reference. BTW be sure there is no residual magnetism in the article.

tom_rochester
Tom Rochester
Plating Systems & Technologies, Inc.  
supporting advertiser
Jackson, Michigan, USA
plating systems & technologies banner ad


May 27, 2020

Q. Hi Tom, thank you for your tips. You and someone early in this thread said when doing this type of measuring, to make sure part is demagnetized or has no residual magnetism. If I am measuring a 4 ft long piece of 1" square tubing, how would you suggest removing or checking residual magnetism?

Bennett Bergquist [returning]
- Rupert, Idaho


May 27, 2020

A. There are expensive ways to do it. But a simple, pragmatic method is to see it there is enough residual magnetism to move a common paper clip. Hold the article contacting the paper clip and see if you can move it.

tom_rochester
Tom Rochester
Plating Systems & Technologies, Inc.  
supporting advertiser
Jackson, Michigan, USA
plating systems & technologies banner ad


May 28, 2020

thumbs up sign Thanks for the idea Tom,
Paper clip should work for me.

Bennett Bergquist [returning]
- Rupert, Idaho

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