Robin,
Not sure what ospho is??? You need to have newly blasted steel surface
cleaned with degreaser and maybe lightly sanded depending on the grit of
sand used. Then use epoxy primer over that. If it has sat a while after it
was blasted (more than 2 days depending on humidity) you need to "etch" the
steel to clean off the powdery oxidization and then wash it with water to
neutralize the etching acid. Dry it VERY well and immediately. Then you
prime with epoxy directly over the steel.
Another option is to clean the metal as well as possible and then use a
"self etching" product that contains an acid that etches the steel. The
problem here is that you are not able to put epoxy over self etching primer
as they are not compatible. You can put a colored product such as Sikkens
Colorbuild surfacer over this but you will need to sand this to recoat it.
The advantage of this is that you can "wet on wet" if it is a dipped surface
as it is possible to recoat it directly with topcoat if you stay in the
recoat window. It is also possible to exactly match the topcoat color so
that chips (when they occur) are not as noticeable. The limitation is that
it does not have the "filling" ability that epoxy has without sanding and
typically you will need to sand it after curing to hide the surface
imperfections.
Epoxy primer is good if you are considering top-coating a rougher surface
with a "wet on wet" application of epoxy primer then after that flashes for
1 hour you are going to paint right over this. This is great for the
interior of the car or door jambs where you do not want to sand the surface
after it is primed. If the surface is rough due to sandblasting the epoxy
does a pretty good job of filling the sand blasted surface so that when the
paint dries it is reasonably smooth. It would not be good enough for an
exterior surface for my discriminating eye but for undersurfaces and
firewalls or even suspension parts it is more than acceptable and INCREDIBLY
durable.
All of this info relates to Sikkens products and I can not vouch for the
ability of our competitors products to perform the same.
Best Regards,
Tim Ronak
Business Development Manager
Akzo Nobel Coatings
OFF: (949) 305-5393
VM: (800) 234-6747 ext. 2257#
-----Original Message-----
From: Robin Young [mailto:robin02@mindspring.com]
Sent: Wednesday, April 24, 2002 9:41 PM
To: Ronak, TP (Timothy)
Subject: Re: Dipping or blasting
Tim, I have blasted some large parts but plan to dip the chassis. Tomorrow
I plan to use osopho on the parts that are ready and intend to epoxy prime
over that. Is this the etching you are referring to or am I off track
thinking that primer can go on top of the osopho?
> Dan,
> Be sure that you have whoever does your car use a self etching and
> non-sanding type of "primer"
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