<VV> Artzberger on Painted Hexes

[Kirby Smith]

Jeff Schramm wrote:
> The "metal cleaner" is probably just any degreaser. One example of the
> "metal conditioner" that leaves a zinc phosphate coating is
> Metal-Ready from the good folks at POR-15. The same stuff is available
> from other vendors but I don't remember the generic name for it.
> 
> On 4/18/05, N. Joseph Potts <pottsf at msn.com> wrote:
> 
>>OK - now we've got it down to brushing instead of spraying, the next
>>question: primer, or no primer. Artzberger's tip recommends certain
>>chemicals I don't have at the moment, but I'm looking for them. Do you use
>>these, paint bare metal, or use primer?
> 

Generally, for automotive body (steel) painting, one cleans the surface 
of grease with a suitable degreaser, cleans with a phosphoric acid etch, 
passivates with zinc phosphate mix, then primes.  Shortcuts are often 
taken by people in the trade who aren't painting their own cars.  (Which 
is why I had to go out of my way recently to get zinc phosphate mix.) 
All of these chemicals are branded by the major auto paint companies 
(PPG, Ditzler (if PPG hasn't fully absorbed them yet) DuPont, etc.), and 
some second tier brands.  Check their websites.

There are paints which are either self etching, or which seem to work ok 
without much preparation.  I believe Clark's engine sheet metal paint 
asserts it can go on bare metal, and while I've never primed before 
using it, I do use the other steps.

With zinc phosphate, you just want a gray color to form, not a bunch of 
large crystals on the surface.  Generally, a hour's soak is required for 
the latter, so wiping a difficult to reach bolt head is unlikely to get 
that much solution on the bolt.  Dry thoroughly afterwards.  Dry zinc 
phosphate passivated steel will last for years without rusting.

I have used these steps to completely derust and passivate fasteners, 
but only for non-critical ones, as the acid solutions very likely are 
causing hydrogen embrittlement of the threads.

kirby