Shoddy workmanship occurred and it's been eating at my conscience.
It's visible in this photo I posted previously, despite efforts to hide it with camera angle.
Enhance
Enhance
There it is - coating failure due to poor adhesion.
I painted these several years ago before gaining a better grasp on automotive refinishing and gained a lot of respect for professional refinishers and coating technology in the process.
The shock towers were originally bare zinc plated, similar to those below. I like the open design with easy shock access, but didn't want the bling.
If I recall correctly, I simply hand sanded them down before spraying with an unknown rattle-can white primer and then some unknown rattle-can black satin.
Mistake #1: Improper prep - Hand sanding was insufficient. Also likely didn't degrease the metal properly.
Mistake #2: Spraying black over white primer - Any intercoat adhesion issues will be very obvious.
Mistake #3 : Spray paints are cheap and convenient but mediocre in terms of qualities such as adhesion, sealing, UV resistance, durability, and leveling. There are a few decent products, but they're the minority.
Time to atone for my sins. The first step was to strip every last bit of paint. The process went like this:
- Chemical paint stripper
- Wait
- Reapply paint stripper
- Scrape paint off
- Wash off paint stripper
- Dry
- Degrease
- Dry
- Lightly etch in media blaster
- Blow dust off
Result, ready for coating.
What to coating to use? For bracketry and such I normally start with epoxy primer and topcoat with an alkyd enamel, but in this case (and the foreseeable future) I'll be using what is IMO the highest quality solution available to DIYers: SPI epoxy primer and SPI matte black SS polyurethane. Even better, I even happen to have it on hand - leftover from painting the chassis.
Quality alkyd enamel is good, but urethane is great, if you have the equipment to spray it effectively and safely (isocyanate exposure). Normally, SPI's Matte black SS is used on bodies of high end restorations. For example:
However, it has two additional qualities that make it a great high-performance option for coating parts too:
- Gloss is fully adjustable simply by changing the activation ratio
- It's a single stage paint. No need for clear coat.
For the chassis, I used a 4:1 activation ratio. It was close, but I was left desiring just a bit more gloss. (This pic shows more gloss than it achieved after full cure)
This time I tried a 2:1 activation ratio, but I think that overshot the mark a bit. In the future I'll be mixing at a 3:1 ratio which should give that perfect OEM semi-gloss.
Atonement complete. Happy Thanksgiving.