When you spend a lot of time, effort, and money on something, it's only logical to protect it, right? We think so, especially when that time and energy is spent on a car that you plan on keeping for a while. Such is the case with the '55 Chevy chassis in our "Framing A Classic" series.
After having new brackets and crossmembers welded to our frame, plus trial-fitting the rear suspension, we decided the next logical step was to give it some sort of protective coating. Why do it at this point? Well, since we were finished welding parts to the frame and anticipated adding only bolt-on components in the future, it wouldn't have made sense for us to bolt up the front suspension, only to take it all apart again to paint or powdercoat the frame.
Given the parameters of our project-a ground-up effort that's scheduled to see plenty of street duty when it's finished-powdercoating was a logical choice to use for a protective finish. Most of you are probably familiar with the process, but here's a refresher for those who aren't. Powdercoating is a means of protecting metal parts by coating them with a durable, plastic-like coating (typically polyester, epoxy, urethane, acrylic, or a hybrid of those materials). The thermo-set plastic starts out in powder form and is sprayed through a gun that gives it a static electric charge. This charge makes the powder cling to the part you're coating, since the part is electrically grounded during the process. After the powder is applied, the parts are baked at a high temperature (usually between 375 and 400 degrees Fahrenheit, with varying times depending on the part). This curing process essentially melts the powder and bonds it to the metal.
Although the process is a little more involved (and more expensive) than painting, the main advantage of powdercoating is its durability. The finish is extremely tough and more resistant than paint to such common automotive hazards as rock chips, scratches, fuel stains, and other potentially damaging fluids. Powdercoating is also easy to clean and maintain, and in recent years has become available in a wide array of textures and colors (even some candies and metallics), making it easy to match (or accent) the painted surfaces on your car.
Just like a quality paint job, successful powdercoating begins with plenty of prep work. You want to catch flaws before parts are coated, because stripping powdercoating off a part is not easy or enjoyable. For our frame, initial preparation came at Williams Classic Chassis Works, where the crew cut off unneeded brackets, fixed broken ones and, in general, made the frame more presentable. Absolute perfection wasn't their goal, because that isn't our objective with this project. We want a chassis that will withstand the elements while being easy to clean and maintain, not an all-out showpiece that's going to be displayed on a pedestal with mirrors underneath it. Therefore, a little bit of pitting (left over from heavy surface rust) and a few miscellaneous dents were acceptable to us. Minor flaws like these could have been fixed, but we didn't feel the need to spend the effort doing so.
In addition to fixing visual flaws, parts to be coated need to be stripped of old paint and rust. The best way to do that is usually to have them media blasted. Though our frame had been blasted before we started the build-up, it needed a touch-up before we sent it to off the powdercoater. So we hauled it over to Polyrock, in Chino, California, to have the surface prepared. The crew at Polyrock blasted the frame with Green Diamond, a mineral slag abrasive that cleaned up the remaining rust and gave the surface a good texture for the powder to adhere to.