Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
-----
Electrical effect on adhesion in plating tank
October 7, 2016
Q. Good morning,
My question is in regards to adhesion. I am well aware of the cleaning prep work necessary to get good adhesion. My question is in regards to the electrical portion of the plating process.
What electrical anomalies could cause delamination of plating. I'm applying a heavy layer of bronze. Occasionally, we get a plated piece where the plating looks really good, but any small amount of force will cause the plating to lift off.
I know the cleaning process is sound. For example, we will have multiple racks cleaned at the same time, through the same process and plate at the same time, but on different rectifiers. One rack will fail but the others will have beautiful adhesion.
What should I be looking for with respect to power / rectifier anomalies that may cause this 'lack of adhesion' condition? We're using some older equipment, but we have checked ripple and they are all within limits. Could there an incoming power source issue? The rectifiers haven't tripped off or anything. We have had peels issues in the past with power outages (i.e. storms, etc.) and have generator backup now.
These instances are not occurring when any (obvious) electrical issues occur. What are some areas of my system that I should inspect?
Thank you in advance!
Dawn
- Bellaire, Michigan USA
A. Hi. Interesting question, Dawn.
I have seen and heard of current interruptions causing laminar plating in nickel and chrome. I'm surprised that an alloy like bronze can be plated to even look right if the rectifier is mis-performing though. A few more points of information might help: What is the substrate? Does the plating peel at the substrate or in the middle of the plated layer?
If it peels at the substrate, I'd be prone to questioning your finding that the cleaning is okay. Do you do electrocleaning? If so, I'd lean towards believing that the particular rack did not electroclean properly due to bad contact or whatever.
Is the situation such that someone actually walks the line and is familiar with what actually goes on as opposed to what you hope goes on? :-)
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
October 2016
Q. Hi Ted,
Thanks for the response. Our substrate is soft carbon steel. We've seen both conditions actually. We've had parts peel and it visually looks like the substrate is exposed. These we've attributed to our cleaning process (which we've just exhaustively been improving).
But, we've also had parts that have a double layer of peeling. These are the ones that have us scratching our heads. If we are having current / power interruptions, we can't see what's triggering it. That's what I'm after...where do I start looking for this?
Thanks.
Dawn
- Bellaire, Michigan USA
October 7, 2016
A. Is the acid dip preceeding the plating leaving a carbon smut, let's experiment with a milder acid dip. Then let's try a Copper CN strike before the bronze.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
October 7, 2016
Q, A, or Comment on THIS thread -or- Start a NEW Thread