stebharvey@ameritech.net wrote:
> ...snip... applied POR-15 to everything but the exterior. I purchased PPG
> epoxy primer to use as a base coating over the exterior metal. The problem I
> face is that PPG states that epoxy primer MUST NOT be applied over an etching
> primer. It will bubble up and just not stick. POR-15 makes an etching primer
> to be applied directly over the POR-15 as base coat primer. My question is,
> has anyone applied an epoxy primer directly over POR-15? If indeed I can't
> apply epoxy primer directly over the POR-15, I will be forced to use two
> different types of primer and paint, one type for the POR-15 areas and epoxy
> primer on the exterior surfaces. I hope I'm not
> boring the group with this long question.
>
Steve:
Epoxy primer is designed to be your BASE primer. It has it's own etching
properties and as a result will interact unfavorably with other primers. Epoxy
primer is usually used by itself and then gets re-coated with a "fill" primer.
That is a primer with build-up material in order to be sanded off (wet -
sanding). POR's primer (Tie-Coat, IIRC) is designed to "cut" into the cured POR
(for adhesion) and will then provide enough "build" for a moderate amount of wet
sanding.
The whole purpose of shooting Tie-Coat is that normal paints and primers will
not cut in to the POR well enough to provide adhesion, and although you ~can~
sand it, it is a MAJOR undertaking. Once you've coated POR with their Tie-Coat
you should be able to scuff/wet-sand it enough to accept a secondary coating of
a high fill primer (if necessary.
Since you've applied POR to the interior metal, then just top coat it with a
light coating of Tie-Coat and finish it with your color paint after scuffing /
wet-sanding the Tie Coat.
On the exterior, apply your Epoxy directly to the bare metal, allow to cure and
then top-coat that with a coating of fill primer (if needed / desired) and then
color coat.
Treat the two surfaces independently and although you will be using two
different types of BASE primer, you should be able to use the same final primer
for again, the same paint on both surfaces.
Don't be misled about POR. It provides an excellent protective coating over the
metal and if treated properly can be re-coated easily. POR can even be applied
over new metal as long as you prepare the surface properly, that is, degrease it
(Marine Clean) and then etch it (Metal Ready). If you don't do those two steps,
then you're asking for it to lift off and .... it will.
2"
Enrique
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