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Blue Chrome defect in hard chrome plating
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Q. I am a chemical engineer working in a plating shop where we Chrome plated parts, but in these last days during the application of the hard chrome we have many parts with blue Chrome. Any idea what is happening?
Your comments are welcome.
Michael.
- Montreal Canada
April 27, 2022
A. Hi Michael. We'll have to see what someone else says because I have never even heard of such an issue :-(
If you could send a photo to mooney@finishing.com for posting here it might help. Thanks.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 2022
April 28, 2022
A. Hello, Michael,
I've never worked with hard chrome, so I don't have practical experience, but I've read that blue chrome deposits means an iron contamination higher than 15 g/L and that this is more common in hard chrome than in decorative.
In this technical manual I'm reading, it is also written that there are no easy means to remove this contamination, just diluting the bath.
Also, is Hull Cell
⇦ huh?
a common test for hard chrome? If so, it should give you some hints.
Some photos would also help finding the answer to your problem.
Hope this helps you.
Regards,
Chemical Engineer - Nova Friburgo, Rio de Janeiro, Brazil
A. When you say "in these last days", I have to assume you are using the racks over/over without cleaning the contacts?
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
May 27, 2022
May 26, 2022
A. Hi Michael,
Having worked as a lab manger at a functional chrome shop before, I'm sure it isn't critical for functionality. But it is an interesting sort of defect. Are you plating over a different deposit (sulfamate, cad, zinc) or just over steel?
Q. We are running into a similar issue at my decorative chrome shop. The defect appears to be a rainbow iridescence that is VERY distinct only on certain parts (we see it on everything to varying degrees). We have isolated the issue to our Ni anodes but can turn the defect on-and-off with good ol' STEP enhancer. Does anyone have any other ideas as to what could be occurring here?
- Michigan, USA
May 26, 2022
! We identified the problem originating between MPN and electrolytic chrome pre-dip. Here are things we have attempted:
pH low in MPS
pH high in MPS
Carbon treat MPS
Permanganate treat MPS
Low current MPS
No current MPS
High current MPS
No current chrome pre-dip
High current chrome pre-dip
Decant chrome pre-dip
Add STEP enhancer to MPS
The addition of the STEP enhancer to the MPS (causing the nickel to become more noble and risking white wash) has been a quick fix as of late to eliminate this iridescence. The sustainable long term fix was to change out anodes in the MPS. Has anyone else been able to address this issue another way?
- Michigan, USA
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