Newbie questions why plated-in-China nickel and chrome is peeling

A. Hi Larry. We've posted your inquiry, but a hundred things have to be done right for quality plating, so a lot can go wrong, and it's hard to guess which things were done poorly. It is very difficult for a buyer to do the troubleshooting even if they have expertise and can visit the plating shop; you usually have to rely on the plating shop to figure it out. With little expertise and relying on a shop 12,000 miles away, your only realistic option is probably to use a different plating shop. So far we can count on the fingers of one hand the number of technical responses we have received from China. I'll keeping my fingers crossed, but it will be a surprise to me if any Chinese plating shops help you create a list of what quality measures are often skipped in China and what problems that causes.

A. Like a computer-garbage in-garbage out. When you go to the lowest priced vendor you will frequently get the lowest quality. Peeling is caused by poor control of the process. From parts not clean, totank parameters not properly maintained, or poor rinsing, or stopping for too long between critical steps, or wrong process chemicals for the use/part/metal, to mention just a few.

A. I realize you are hungry for answers, so mine may help. First of all, your substrate appears to be die cast zinc, a poor choice for application in vinegar or wine. You parts are probably already plated in nickel with a thin layer of chromium over that to protect the nickel from corrosion. The nickel, not chromium, is peeling. With die cast zinc, I believe that most problems are related to the substrate -- either itself or its cleaning. Plating accentuates pores, it does not fill them like paint. Any porosity in the substrate is a hole where it can be attacked, peeling the plating. There are shops that can make and finish such parts pore-free, but probably not at China prices.

A. Hi again Larry.

1. It's difficult to guess whether they'll all peel, but probably not; probably some got clean enough for the plating to stick.
2. Yes, there are generally correct sequences to follow; most plating texts including the Electroplating Engineering Handbook will list those sequences. But if you read the 15-20 step sequence, you're still left with the issue that all the correct parameters must be held for each of those 15+ steps. Further, as Paul says, zinc diecastings are a poor choice for the application, and careful quality control of the castings is required to insure no porosity or cold shuts.
3. As we've all said, it just won't prove practical for you to issue a list of required process improvements. Sorry.
4. These items are probably vibratory finished, cleaned, acid dipped, cyanide copper plated, nickel plated, then chrome plated. It's highly unlikely that the chrome itself is the problem and that you can fix the problem by focusing on it.
5. Your current stoppers are surely nickel plated, then chrome plated. Skipping the chrome step won't improve their quality.
6. You should ask what the substrate is, what QA tests are performed on it before plating, and what is the exact plating sequence.
Best of luck, but again, you can't solve it -- all you can do is buy from shops that will solve it.

Regards,