Matchthebox’s question about zinc pest in dtg11’s post about his Minichamps Bentley Continental GT got me to thinking about zinc pest and paint rash and whether or not they are related. If you’ve been collecting diecast long enough, you’ve probably seen both these terms, most likely used interchangeably. There is a Wikipedia article on zinc pest that explains the process, however it seems to think that this is a problem of the past. Either the article is wrong in this regard or something else is at play. A simple search for zinc pest will net you plenty of hits in various diecast forums. Most of those threads will refer to that above mentioned Wiki article, but there doesn’t seem to be any consensus as to if paint rash and zinc pest are one and the same. Some think that paint rash is the early warning sign for zinc pest, while others see them as separate issues. I’m no metallurgist, so I won’t attempt an answer here either, but I will try to show the difference between the two.
First up is paint rash as shown on the hood of my own MC Conti GT. It’s difficult to photograph, but it presents itself as little bubbles under the paint, as if the paint was contaminated. The model certainly did not have this when I bought it, and it’s progression to the current state has happened over the 10-11 years I’ve owned the model. I can’t remember how bad it was when I first noticed it, so I can’t say if it’s gotten worse or not, but it’s been like this for years now.
Next up is my Anson Mercedes E-class Estate. Now this is full blown zinc pest. As you can see, the paint on the hood is cracked, and some of it has cracked off while in storage. Not as easy to see is that the hood is deformed so much that it doesn’t sit flat on the car. Move around to the side, and you’ll find my wagon has the rare “Wrangler Door” option ‘cause the hinge broke. And as you can see in the picture, the curvature of the door has flattened out relative to the body, and what’s left of it is too big to fit in the door opening. I’ve owned the Anson about as long as the Minichamps, but it’s an older model. It didn’t exhibit any issues either when I bought it, and I never got anything that looked like the paint rash on the Bentley. Even now there is nothing resembling paint rash.
What can you do to stop this from happening? In either case, nothing. But it seems that paint rash can at least be fixed with a simple polish in some mild cases or a strip and repaint. I’ve seen conjecture about temperature and humidity playing a part, but my Bentley had been on display since day 1 and it was purchased when it was a new release. It’s been stored in the garage for the past couple of years, but the rash was there long before, and I have plenty other models in the same garage with no issues whatsoever. With resin and composite models poised to take over ever increasing chunks of the “diecast” market, I’m sure we’ll soon be reading about the issues those materials bring with them as well. The moral to the story: Liberate your models and enjoy them while you can. Viva la DLM!