Cautionary Tale: sand blasting / bead blasting on body panel

[543fold]

[543fold]

[dawerks]

Live and learn brother! Thanks for sharing your experience. It's one thing to 'hear' of someone doing it, it's alot more important to hear first hand experience.

We all learn from our mistakes! Good to know I'm not the only one who screws up

I obliterated a nice 55 Oval back in the day. I thought I was getting a bargain on sandblasting at only $100 (picked up/dropped off!!). Bug was sent straight to the crusher
_________________
"There is only one sin; disconnection from self."

[martyrg]

I blasted my Ghia vert using the equipment at this company, CONSOLIDATED STRIPPING & DERUSTING, INC. http://www.consolidatedstripping.com I followed their rules listed here: http://www.consolidatedstripping.com/mediablastingrules.html and had no probems. No warping or distortion whats so ever. Sprayed it with DP 90 the following day and all is good.

[baxsie]

[baxsie]

I decided to test the adhesion of KBS RustSeal on:

* Bare metal, cleaned with a power wire brush
* Bare bead blasted metal
* Bead blasted metal, with zinc chromate.

We did each of these on both un-etched samples, and on samples prepared with KBS RustBlast.

Here is what the samples looked like when the paint was wet:

Here is what it looks like after a cross-hatch adhesion test:

My conclusions:

* Using a wire brush only, with or without etch does not get a good bond.
* Bead blasting without an etch does not get a good bond.
* We only saw good bonds on the bead blasted, etched samples.

The zinc plated, non etched sample had poor adhesion, but not worse than the wire brushed non-etched sample.

Etching the zinc sample is useless. The etch takes the etch off:

I might make one more test on the zinc plated sample, after scuffing it.
_________________
1975 LaGrande Super Beetle Build Log / Farm boy hinge pin puller / Farm Boy Chassis Rotisserie
"I'm not getting older, I'm getting bitter."

[baxsie]

I still wanted to find a primer that would go over the Zinc Chromate, so I went to our local auto paint store with a sample and picked up their recommend two component (2K) epoxy primer, DP90LF, along with the activator and reducer:

I used the reducer to wipe a section of a Zinc Chromate plated fender, painted it, let it cure, and did the adhesion test:

I also did a test with no reducer wipe:

It looks like the adhesion was good in both cases, even over the Zinc Chromate.

The finish looks perfect, just the slightest matte:

Frankly I was scared of spraying, but I picked up a Harbor Freight HVLP detail gun, and the folks at the paint store walked me through the mixing, and I am very glad I took the plunge.

At this point I think I have a fantastic rust prevention system: The zinc chromate plated on the bare blasted metal, painted with the DP90LF 2K primer, then it will be topcoated with an 2K industrial coating.
_________________
1975 LaGrande Super Beetle Build Log / Farm boy hinge pin puller / Farm Boy Chassis Rotisserie
"I'm not getting older, I'm getting bitter."