Let's assume you've got a pre-1970 car of some kind (or maybe an early Porsche/BMW/Audi, etc.) which wasn't factory galvanized. You've got it down to a bare metal unibody and all the holes have been filled with replacement steel. Galvanizing isn't a terribly complicated process but I've never heard of anyone having it done. I assume that's because the tank for the frame would have to be enormous. Or would it be the expense? What would be the best rust-proofing process you could do in that situation?
MrChaos wrote:
15 heavy coats of por 15
That would ADD weight to the car, so no. 1 coat should be enough.
Seems to me using an epoxy primer is your best bet. Of course, if it is scratched off rust can start, but it is extremely moisture resistant and durable. If someone is going through all that trouble, then I doubt that's a car that will get driven on salty roads or left outside, so it won't be as vulnerable to rust in the first place.
Would a cold galvanizing spray work?
You would have to find some industrial shop that does galvanizing of large items. A frame wouldn't be so bad (they could dip it in one end at a time) but of course a whole body would need a body-sized tank. Then you'd have to prep it for painting, and industrial galvanizing typically leaves a rough surface and it doesn't take paint very well.
Don49
HalfDork
6/15/14 7:50 p.m.
Self etching zinc chromate primer. It's even sold in aerosols at NAPA. Chrysler considered it the equivalent of factory rust proof for repairs.
international paint strip in romulus mi has an e-coat tank that's big enough for car bodies.
stuart in mn wrote:
You would have to find some industrial shop that does galvanizing of large items. A frame wouldn't be so bad (they could dip it in one end at a time) but of course a whole body would need a body-sized tank. Then you'd have to prep it for painting, and industrial galvanizing typically leaves a rough surface and it doesn't take paint very well.
Oh, you mean like a boat trailer manufacturer?
Where oh where could we ever find one of those ...
Most of those galvanized bodies were done via the electro plating process and not hot dipped. A piece of sheet metal could warp if dipped in to molten zinc which is what hot dip galvanizing is. Plating zinc only requires a large tank big enough to fit the body in the tank.
Jim is right. Hot dip looks like this:
It looks like solder that wasn't applied with enough heat or flux.
Cold galvanizing is a plating process that you typically see looking like flakes. Like this:
Either way, Zinc sucks at holding paint. If you do either process, the prep work will be key. There is sanding (making sure you don't sand through) along with acids, phosphorus compounds, etc. It makes painting anodized aluminum look easy.
Spray cans of "galvanizing" paint are basically paint with powdered zinc in them. They are not anywhere near the durability of an electroplated zinc surface. They will only be as durable as paint.
So... either plate it "right" or just use paint and save your money.
jimbbski wrote:
Most of those galvanized bodies were done via the electro plating process and not hot dipped. A piece of sheet metal could warp if dipped in to molten zinc which is what hot dip galvanizing is. Plating zinc only requires a large tank big enough to fit the body in the tank.
Like a crappy above ground pool?
(wait, are we back to the rust-removal thread again ...?)
Maybe you could do rust removal first, then reverse the polarity and plate zinc over the now freshly de-rusted and etched steel.
Don49
HalfDork
6/17/14 8:02 a.m.
As a former factory paint rep, I repeat: self etching zinc chromate primer. It's easy and effective. Chrysler would not have accepted it as a suitable replacement for factory rustproofing if it didn't work.
Don49 wrote:
As a former factory paint rep, I repeat: self etching zinc chromate primer. It's easy and effective. Chrysler would not have accepted it as a suitable replacement for factory rustproofing if it didn't work.
The aircraft industry is also on board with this. Look at any plane. IF it's not polished it painted with zinc chromate.
Don49 wrote:
As a former factory paint rep, I repeat: self etching zinc chromate primer. It's easy and effective. Chrysler would not have accepted it as a suitable replacement for factory rustproofing if it didn't work.
judging from the alarming amount of rotted out 5 year old chrysler products in my area, i would do the opposite of anything they accept or recommend.
