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Paint Shop Tech. Talk about paint removers, thinners, primers and application techniques plus related topics. Rust removal, paint substitutes and color matching.

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Self Etching Primer


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  #1  
Old 04-09-2011, 09:15:59 PM
shortkid shortkid is offline
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Default Self Etching Primer

Just what does self etching primer do over regular primers?
thanks
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Old 04-09-2011, 10:47:00 PM
jwx3 jwx3 is offline
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Default Re: self etching primer

The primary purpose of a etch primer is corrosion resistance
With adhesion being the other advantage the only problem with most
Self etching primers is that you should use either a sealer or a primer over top of the etch primer.
In my opinion etch primers don't work that well over cast iron
Epoxys or mastic primers work better and are generally cheaper
And can be top coated with out the use of sealers.
Just my 2c worth
Jim
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Old 04-10-2011, 01:23:14 AM
jht1057 jht1057 is offline
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Default Re: Self Etching Primer

NAPA has a really good self etching primer, it is in their finish one line. It does not need a sealer before the finish coat and corrosion resistance is excellent.

I use this product on all of my projects, cast, steel, stainless steel, aluminum and even wood.

It can be wet sanded for a mirror finish coat.

Just my 2 cents.

Jim
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Old 04-21-2011, 12:11:26 AM
Jim Alexander Jim Alexander is offline
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Default Re: Self Etching Primer

Hello Jim, I'm dressing up a Stuart S50, do you feel this would be the perfect primer for this piece? Any advise on spray paint type and brand.
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Old 04-21-2011, 11:50:13 PM
jht1057 jht1057 is offline
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Default Re: Self Etching Primer

I believe it would be a good primer for your project, NAPA would also be a source for your paint as well. I spray a lot of urethane paints, in your case an acrylic enamel would be a more authentic finish.

Jim

---------- Post added at 11:50 PM ---------- Previous post was at 11:47 PM ----------

NAPA's paint line is dimension made by Sherwin Williams, PPG has a bargain line as well. I have sprayed both, either is fine.

Jim
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Old 04-25-2011, 09:58:10 PM
BarryMc BarryMc is offline
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Default Re: Self Etching Primer

Most epoxies now days are self etching. I would recommend using epoxy instead of the old green self etching primer.
1) Epoxy Primer is a two part primer consisting of the primer and an activator.
2) Epoxy primer is used as a direct to metal primer (DTM) because it has excellent corrosion resistant properties.
3)Depending on the brand it also can be reduced and used as a paint sealer. Also depending on the brand used there are several colors available such as black, white, gray, green and red.
4)Epoxy primer works great over freshly sand blasted metal. It is not meant to spray over rust, the metal must be properly sanded or blasted and clean.
5)Epoxy primer will adhere to all properly prepared metals. I have used it on steel, stainless steel, aluminum and brass.
6)It can be used underneath body filler.
7)Some epoxies can be painted over without sanding within a certain time window. The brand I use has a 7 day window. Best advice I can give you is to read up on
the product that you are going to use and to wear the proper safety equipment.
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Old 05-12-2011, 01:28:00 PM
DieselAddicted DieselAddicted is offline
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Default Re: Self Etching Primer

To understand the whats, whys and where used of self etching primer you need to understand why the underlayment needs, or does not need chemical etching to begin with. No matter if performed mechanicaly (sanding, sandblasting, wire wheeling) or chemicaly (acid), etching is done to promote adhesion of the coating to the underlayment. Now, to understand why self etching primer is not an all purpose all situation primer requires a person to understand that the best paint coating bond you can get is a chemical bond, not a mechanical one. BUT, A chemical bond is not possible when dealing with bare metal or old, fully cured coatings. The best we can do is a mechanical bond, or etch. Simply put we put scratches on the old surface so the overlay can seep in the scratches and provide a toe hold for the new coating, also known as "toothing in". If you have sanded to anything coarser than about 400 grit, sand blasted or wire wheeled your parts then they were etched when you got done. If you have new sheetmetal that does not need sanding otherwise then self etching primer can be used to save some labor as the acid will etch the steel. The acid used has no effect on cured paint, fiberglass, plastic, stainless steel, or any other non plain steel surface so it in effect does nothing. BUT does it hurt? Contrary to what some write self etching primer can indeed be a detriment to the best bonding of your paint layers due to not being fully compatable with the underlayment or the top coatings. I would never use it contrary to makers P sheets on a job that had to be both right and last.

So here is the skinny:
1. Chemical bonding is best
2. When that is not possible we must etch.
3. If you have sanded you have also ecthed.
4 Additional ecthing adds nothing
5. Best bonding both directions, to etch, and to compatable top coats will be with epoxy primers.
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