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modas 01-12-2006 06:22 AM

Brand of weld thru primer
Hi Guys -

I'm getting close to starting the inner/outer rocker work on my Impala. In fact, my new pieces should be arriving tomorrow :D. Anywho, my plan was to spray the inside surfaces of the inner/outer rockers with a spray bomb weld thru primer from NAPA. I think (if I remember correctly) it was heavy in zinc and created kind of a galvanized surface.

My other thought, was to mask just the areas that were going to be spot welded the epoxy prime everything else, THEN remove the mask, mask the expoxy primer, then spray the rest with the spray bomb weld thru.

Would the spray bomb weld thru primer give me sufficient protection or should I be doing this differently? I certainly don't want to do this again in 10 years :D

Much Thanks!


Thanks for the help

chadsbodyshop49119 01-12-2006 06:31 AM

IMO.. your much better off with the epoxy.. weld thru is porous untill you get it hot.. so it doesn't help much except around the area's you weld.. i'd suggest self etch if you must spray bomb... but still say epoxy is better.. if you must spray bomb.. the wurth seems to work about the best imo.. and they have the same product labeled as specialty.. if you can find it good luck..

baddbob 01-12-2006 07:29 AM

I usually epoxy the inside of all parts then go back and clean the epoxy off of the weld areas and apply 3M weld through coating, use the stuff in the purple labeled can, then when she's all done go back in with a 360 degree spray head wand and coat the inside of these areas with a cavity wax, 3M's Rust fighter, Transtar's Amber coating. I recently heard Amsoil has one out that's top of the line with good creep and wax content but haven't tried it yet. bob

MARTINSR 01-12-2006 07:59 AM

I'm with the others, "weld thru" primer is for, well, "welding thru" :) It has VERY, VERY I mean V-E-R-Y POOR adhesion qualities. It is for the mating surfaces only. The "pinchweld" area where the edges of your rocker meet at the bottom, JUST where they meet, and will be plug or spot welded, that is what weld thru is for.

And don't use the NAPA, it is way too thick. Get some 3M or better yet, SEM. Use it sparingly and let it dry real well before you try to weld thru it. Be sure to cut off the mig wire with every weld so when you start you have a nice new, sharp tipped wire to spear thru the weld thru.


modas 01-12-2006 02:05 PM

Hi guys -

Thanks for the responses. A couple of more questions that I've generated from your answers and from going down to the local shop. It seems I don't know what I think I know, at least according to the guy at the shop. I had more questions for him, but he was starting to get annoyed with my questions when he realized I wasn't going to buy anything right then and there.... This is going to be kind of a long post, so bear with me... :)

This is what I thought I knew.

1. Bare metal. - Spray with epoxy primer. Can use straight epoxy primer, but required an etching step prior to application, OR you can use a self etch epoxy and skip a step. Once sprayed, the metal is seal and you are done. Nothing else needs to happen. Metal protection is the same between the two types of epoxy primers.

2. IF the epoxy is sprayed on metal requiring body work (body filler) and a BC (like on body panels), the body filler is applied to the epoxied metal, and when everything is ready, the Urethane primer is sprayed so the BC/CC has something to stick to (plus the urethane is easier to work with)

Now, what the guy at the shop said, was that epoxy primer could NOT be left by itself. It had to have a Urethane primer sprayed on it which just didn't seem right to me. So, which is it? Can I leave the epoxy primer alone, or do I need to put the urethane over it as well.?

The shop had a self etch epoxy primer. The brand name was NASON which is supposedly made by DuPont. The only epoxy name I recognize is SPI. Is the Nason stuff any good or is it all pretty much the same? The straight epoxy primer (requiring the acid etch) brand name was called kwik cycle (by transtar autobody technologies). Any comments on this stuff?

My plan, was to use the epoxy primer by itelf on all the interior sheet metal that would not get any paint or bodywork. Internior metal (truck, rear trunk shelf, etc) which would get paint would get the epoxy, urethane and then the correct paint color for the car. I'm looking to you guys to straighten me out (like a bent piece of sheet metal ;) ).

Its hard to ask questions, when you don't know the questions to ask. Thanks as always for the help!!


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