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topic 47037

Chromate conversion on cadmium not adhering

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A discussion started in 2007 but continuing through 2018

2007

Q. We have a steel stamping that is cad plated with chromate conversion- it is then painted.

We have problems with the paint coming off and it appears to take the yellow conversion coating with it. Any ideas what could be causing this? It appears the conversion is not adhering to the base cad metal.

Joe Arnold
machine shop - Falconer, New York


2007

A. I don't think you can efficiently troubleshoot this problem from your position or we from ours, Joe. I think you need to make contact with the plating shop and have them help figure out what's wrong. It could be excessive brightener, and the next batch could be just fine; it could be an unsatisfactory attempt to substitute trivalent chromating and the problem won't go away. A lot of possibilities :-)

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


simultaneous 2007

A. I've seen problems like this arise both from excessive brightener, as Ted suggests, and from poor post-plate rinsing.

If it's the latter, a dip in 1-2% nitric acid before the part goes in the chromate might help. And, of course, using cleaner water.

dave wichern
Dave Wichern
Consultant - The Bronx, New York


2007

A. Joe - Falconer isn't all the far from Syracuse where my shop is located. It would be a whole lot easier to see the actual hardware that is exhibiting the problem (if at all possible before and after painting). I'd be willing to do so if you're willing to send in a couple of parts to review. People like to point their finger at the plater, but contamination post-plating is a likely cause as well. Have you gotten good parts in the past? Have you changed painting houses? How long was the lag between plating and painting? Do the parts require embrittlement baking between plating and chromating? There's a lot more to solving this issue than "why is the paint coming off?"

milt stevenson jr.
Milt Stevenson, Jr.
Anoplate Corporation
supporting advertiser 
Syracuse, New York

Anoplate banner


2007

A. Ted,
Trivalent chromate on cad? I am yet to hear of such a product. I have had several people asking about one but know of none. Part of the reason is economics, a small market.

That being said, Joe, make sure the plater is actually plating the cadmium you have specified and not substituting zinc. There are not too many platers who still plate cadmium due to lessened demand and the toxicity of the bath components.

Gene Packman
process supplier - Great Neck, New York


2007

thumbs up sign No, I haven't heard of a trivalent chromate designed for cadmium, Gene; my thought was perhaps the plating shop is trying to apply a trivalent chromate to cadmium that wasn't meant for cad and that's why it's not adhering? :-)

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


2007

A. I think there is no need to chromate at all if a topcoat of powder or paint is being used. Cadmium is used because it forms its own oxide topcoat which retards further corrosion, unlike zinc that corrodes away.

It might be worthwhile to see if a light phosphate over the cadmium would work better.

Khozem Vahaanwala
Khozem Vahaanwala
Saify Ind supporting advertiser
Bangalore, Karnataka, India

saify logo



June 13, 2017 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. The passivation done after cadmium plating is coming off on simply rubbing with cloth.
Can somebody please suggest remedial measures?

Thanks & Regards

sahil arora
- kanpur, india


August 8, 2017

A. Hello Sahil!

Usually if you can remove the chromate with your fingers or a cloth, there are two big possibilities:

-Organics in your cadmium/zinc bath are too high.
-Concentration of the chromate bath is too high.

This two possibilities have a relative probability that depends on each facility and methods, so please explore them and let us know what you find!

Best regards!

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



November 26, 2017 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hello all,

I have a small cad plating tank for doing small parts. Everything was working very well until I lost my finish gold dip bucket; it cracked and leaked out.

After getting more gold dip and mixing according to the recommended ratios, same as before, I cannot get the gold to stick.

It will coat evenly but wash off.

The cad seems to be coming out nice and bright; just cannot get the gold dip to adhere.

Chip W [last name deleted for privacy by Editor]
- Memphis, Tennessee USA


November 2017

A. Hi Chip. I am guessing that when you talk about 'gold dip' you are referring to a yellow or gold colored chromate conversion coating designed for cadmium plating. So we appended your inquiry to a thread about that problem.

Daniel has given you two good possibilities, and your statement that "the cad seems to be coming out nice and bright" might be a clue that you have too much brightener (organics). But it is not quite clear to me whether you are attempting to chromate conversion coat freshly plated parts and it no longer works, or whether the problem might be that after you got a replacement container and replacement solution and made up the process, you are now attempting to chromate conversion coat cadmium plated parts which you plated some time ago (before the leak); if that is the case, the surface may no longer be active enough for reliable chromating anymore.

(It's not clear whether you are a small industrial plater or a hobbyist. Since you didn't mention catching the leaked solution in a secondary containment vessel, perhaps it's the latter. If so, I hope you have researched the toxicity of cadmium and hexavalent chromium; they're bad ones).

Luck and Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



Discolored yellow chromate on cadmium plating

November 14, 2018

Q. First of all, I am a layman to industrial plating. However, I am really keen to solve the problem I am having now.

Problem:
Recently, my customer complained to us that the connectors they received from us found discoloration of yellow chromate. (Our company does not produce the connector, we assemble wire on it) The connector is finish in SAE AMSQQP416 [link by ed. to spec at TechStreet] Cadmium Plating. I did not find any standard for chromate treatment such as thickness, adhesion, corrosion resistance, etc.

Question:
What is the possible root cause of the discoloration of yellow chromate, or it is normal?

Corden Leong
Quality Engineer - Kuala Lumpur, Malaysia


November 14, 2018

A. The plater did not neutralize off the cyanide before entering the yellow chromate.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina
Editor's note: Mr. Probert is the author of Aluminum How-To / Aluminio El Como
and co-author of The Sulfamate Nickel How-To Guide


November 16, 2018

Q. Hi Sir, I uploaded some photos, could you please look into it? There are some large scale of yellow chromate peeling off from the surface. 47037-1a   47037-1b   47037-1c  

It is the same as what you mentioned?

Leong Corden [returning]
- Kuala Lumpur, Malaysia


November 2018

Trouble in Your Tank: Handbook for Solving Plating Problems
by Larry Durney

from Abe Books
or
info on Amazon

A. Hi Leong. There is a good chance that Mr. Probert is right. But there are other possible causes including the chromate being dried at high temperature (above 140 °F / 50 °C) before it has fully cured.

The components are not satisfactory in this condition, but in truth for a third party to figure out what an unseen/unknown plating shop is doing wrong -- without benefit of walking the line, chemical analyses, examining the records, or even holding the actual parts -- is problematical. It's fine when a plating shop asks for help in this public forum, and they can practically follow up on suggestions and offer ongoing feedback; but when a buyer wants us to look at pictures and, through him, tell the plating shop what they are doing wrong, the likelihood of it working is honestly extremely low :-)

Your postings and your efforts at learning are very welcome! I'm certainly not trying to discourage you! I'm just forewarning a self-declared "layman" that trying to solve plating problems that way is extremely hard rather than easy, and usually just wasted effort. Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


November 23, 2018

After discussion with our customer we found in their final process after the connector assembled on PCBA it will be sent to cleaning.

Cleaning Process Parameters:
Cleaning Fluid: DI Water
Fluid Temperature: 150 °F
Spray Pressure: 75 PSI
Spray duration: 12 Minutes

Does the above process cause damage to the surface? And why?

Leong Corden [returning]
Quality Engineer - Kuala Lumpur, Malaysia


November 2018

A. Hi again Leong. I am not quite following ...
Are you asserting that as long as the components are not cleaned the chromate discoloration does not occur? If that is true, that's helpful data! The large splotch of missing chromate does in fact look like poorly adhered chromate that was pressure washed off, and pressure washing a poor coating can certainly partially strip it.

But if you're saying there is no data available about whether the discoloration occurs before or after that final cleaning, and you want me to guess about whether the final cleaning is the cause, a contributing factor, or unrelated ... no thanks :-)

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


November 26, 2018

Q. Hi Mr.Ted,

Sorry for the incomplete information.

For your question:
1. If you see above 2 pictures large area of chromate peel off. This is happening all after this cleaning process.
2. Bottom 1 picture chromate peel off at the edge, it happens before the cleaning process, the yield rate is 1.37% (5 of 364 pieces). But all happen at the corner or edge area.

Can you guess the above situation?

Leong Corden [returning]
Quality Engineer - Kuala Lumpur, Malaysia


November 2018

A. Hi Leong. You must solve the defects that arise before the post-cleaning process before you worry about whether the post-cleaning process causes additional defects. Yes, the pressure washing is apparently knocking some of the chromate off, but until you are producing good parts that have sufficient reliability & adhesion that the parts do not spontaneously fail, it's a waste of time to worry about whether the post-cleaning is too aggressive and making it worse.

What did you find out from the plating shop about neutralizing the cyanide before chromating, and about the drying temperature? Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



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