Plating Problem

A. John, your question is too broad until you tell us:

• What is the substrate: steel, brass, plastic, zinc, aluminum, stainless steel, etc.?
• What metal(s) are you trying to plate onto it: zinc, chromium, silver, etc.?
• What mechanical pretreatments are you using?
• What is your chemical pretreatment sequence, etc.?

Please get back to us.

A. Ted is right, you will need to get more specific to get a good answer. Potential causes of bad adhesion will depend on the situation. Here are a few causes of bad plating adhesion that I know of: Electroplating always includes a cleaning process. This often is a combination of a cleaner/degreaser, and electrocleaner, and an acid etch. If the parts do not get sufficiently clean, then contaminants can prevent the plating from making a good chemical bond to the metal and can later flake or peel off.

My company often bends plated tubing. We sometimes will get plating that flakes off the tube. We investigated and found out that if plating thickness is too high, then the tube will act like an icy tree branch and the plating will crack away.

The third case I can think of is with plating bath maintenance. One of the additives that platers sometimes add to zinc plating baths is called a brightener. A brightener does what you think, it helps brighten plating. The big problem with brightener is that it is organic and can't easily be measured for concentration. That means a plating bath may become too concentrated with brightener. Too much brightener causes delayed flaking of plating. The nasty aspect is the delay. In this case, a plater will ship nice parts and the customer later opens up a box, sees the plating flaked off, and gets enraged that a plater would let horrible parts like this pass quality checks.

"Electrodeposition: The Materials Science of Coatings & Substrates"
by Jack Dini

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A. Hi again, John. Tim has given you a great start with three roads to travel. But responses from strangers on the internet will not comprise the authoritative source you'll want to quote for such studies. Please try to get hold of a good electroplating book. For the specific issue of "Adhesion", I recommend Jack Dini's "Electrodeposition".
... which has a chapter by that title investigating the science of the matter. Good luck.

Regards,