“I’m in the process of restoring an Austin Mini Cooper. The car has front and rear subframes which hold the drivetrain and suspension pieces. I’d like to powder coat the subframes primarily to protect them from rust, as they have areas that tend to trap water and mud, as well as to ward of chips from road debris or damage to the finish from oil or gas.
I would like the finish to be a semigloss black. What material and/or process would you recommend?
Would it be necessary to mask off threaded holes, or can one just run a tap into it to clean out excess material?
If masking is necessary, what’s the recommended procedure to best withstand the heat?
Also, could you explain the Faraday Cage Effect and how to avoid it, as the subframes have numerous corners inside!”
“The best powder coating material to use is epoxy, for its chemical and chip resistance. Be aware that this material is not UV stabilized and will chalk over time if exposed to UV light. If UV stability is required, then I suggest that you use a polyester material, which is stable under UV light conditions and will not chalk, but has some reduced chemical resistance when compared to epoxies.
The procedure that I would use is to sandblast the entire frame and pretreat it with an iron phosphate chemical using a spray wand system. After the frame is completely dry, powder coat it completely with about 2 to 3 mils thickness. The frame must be put into an oven to cure the powder coating for 20 minutes at 375+ degrees F.
Operator techniques are the best way to overcome Faraday areas. I wouldn’t worry much about them, since you can always touch-up those areas with liquid paint after the powder has been cured.”