Etching primer, etching primer, etching primer!!!!
I keep hearing about people using etching primer for everything.
From all the factual information that I've found it really only
has limited use.
Fact: It contains a small amount of phosphoric acid, which is
what does the etching. In addition to the resins it generally
contains zinc chromate to inhibit rust. It should be applied
thin under a primer and surfacer. If the metal you have has
been media blasted it is deeply "etched", no need for an
etching primer. If the sheet metal is stripped with a paint
stripper and is smooth, an etching primer is appropriate.
Phosphoric acid and iron form an iron phosphate layer on the
surface, of the metal. In spite of what the YouTube videos tell
you, phosphoric acid will not etch plastic such as fiber glass
or plastic body fillers. These are also porous and can hold the
etching primer (phosphoric acid) which has not been converted
to a phosphate and cause adhesion problems when the primer or
surface is applied. Etching primer is an excellent choice for a
bare lower body panel that has been repaired or replaced. Most
factories are treating the body panels with phosphates and some
are using galvanization.
Again, sand blasted metal is heavily etched already and gives
plenty of tooth for the primers to bond to.
Now, my thoughts on frame paint or paint for the accessories.
I've used Rustoleum Enamel for more decades than I care to think
about. I would not use it as a finish coat that is exposed
directly to the elements such as the body. But I've used it all
around in areas the are somewhat out of the sunlight.
All of these "black things" under the hood and the frame and the
under carriage and drive line have been painted with Rustoleum
satin black directly over the bare metal and have lasted for
nearly a decade and a bit over 10,000 miles of fair weather use:
http://www.pbase.com/dennygraham/image/153349409http://www.pbase.com/dennygraham/image/153349410If....my truck was being used as a daily driver where it would
be driven in all sorts of weather, I would prime the frame and
under body panels with an epoxy primer such as PPG's DP90LF,
which would be adequate in itself for decades:
http://www.pbase.com/dennygraham/image/153350700If I was considering placing mirrors under the truck to show it,
I'd topcoat the DP90LF with an enamel top coat.
I've seen wonderful results using POR-15 and Chassis Saver and
they are very durable but can't for the life of me figure out
why they can't formulate it with a UV inhibiter. Makes no sense
to me that it has to be recoated with paint after it's applied.
The brushed frames look just as good as the sprayed frames with
POR-15.
Denny Graham
Sandwich, IL