The Stovebolt Site Forums The Shop Area Paint and Body Shop POR-15 over weld pinholes

I am trying to finish up welding the roof on my cab. I cut it off just below the drip rail across the back panel. I have a cheap HP mig welder & its taking forever to weld it in. The welder makes a mess and is hard to get a good bead, so it had a lot of small pin holes. Rather that keep re-welding & grinding, I was going to paint it with POR-15 and then do my plastic filler work over that to smooth out the area. Since POR-15 is supposed to encapsulate the metal I thought I would use that to prevent rust through & bubbling the filler later down the road. Any Ideas on this????

use phosphoric acid first and/or a good metal prep to neutralize the contamination in there .... I wouldn't use filler over POR15, I don't think it would stick to the gloss very well, better on the treated bare metal

Bill

You need por patch or the epoxy putty.
I know the putty will do it.
You can wet your finger and slick it out real nice.
Looks like they have a couple of choices http://207.97.241.136/PRODUCTS/PUTTYFILLERSSEALERS/tabid/60/Default.aspx
That RESTOGRIP BODY FILLER looks interesting. I have never used it.

I am going to call the people at POR-15 tomorrow & ask what they recommend.

Alan's 57,


I'll bet they recommend one of their products!

Stuart

I bet if you have a credit card, they can ship it as well.....

O.K., I guess I need to speak a little more clearly here. I should have said: I think I will call the people at POR-15 and ask them which one of their products they recommend to use in this situation.

I did call them today and was told the regular POR-15 rust encapsulator would work fine over the holes and could use regular plastic filler over it and it would not rust through, just make sure its cleaned/prepped properly. I guess I will find out if he was right.

Alan....I would hazard a guess that as long as you seal the pinholes from exposure to air/moisture,i.e. POR-15 inside and top coat outside you shouldn't have any probs.
Just remember though,if you just prime the outside after filling,primer is porous and will allow moisture in.
Best to get the paint on as soon as possible!

The best solution is to get rid of the pin holes with weld. Grind around them so you got a good smooth surface then weld up the pin holes . What I do is put a light behind the panel I'm welding so I can see the light shining thru the pin holes. Another suggestion is to do your grinding as you weld some sections instead of doing all your grinding at the end. This also helps keep the heat down and will help in preventing panel warpage. With no pin holes your plastic body filler will last forever, because there will be no possible way of moisture coming thru from the backside of the panel.

[quote=wbrowne] What I do is put a light behind the panel I'm welding so I can see the light shining thru the pin holes. Another suggestion is to do your grinding as you weld some sections instead of doing all your grinding at the end.uote]

That is exactly what I have been doing on all my other panel welds up to now. I was just getting tired of all that welding & re-welding so I wanted to find out if it would be a problem leaving some holes. With the materials they make today, like POR-15 why waste time if its not necessary. When I worked in bodyshops 25 years ago there were no products like what is available today to bond panel, prevent & stop rust etc.I do, however want to make sure its done right the first time because doing it over a couple years down the road will be a lot harder than doing it right today.

i'm a novice at this so take this suggestion with that in mind but why not just clean it with some type of metal prep cleaner and then use something like all-metal or duraglass as a base and then your regular filler over that?................dave

That's what I was wondering too

From experience I would not use por on any exterior surface.As for pinholes,WELD THEM or? duraglass or allmetal press into clean holes well (no air pocket).

What bad experience have you had with POR-15?

You can fill pinholes with POR15. I've done it myself, and it you do it right, no filler needed! I've used it on exterior suraces (the entire chassis, front and rear bumpers, hitch, bedsides and cross sills) and it's holding up fine. The only real complaint I have is that the Chassis Coat Black didn't do as well under the UV as I would liked it to have.
Now, back to filling, I used POR15 as a base coat on a used bumper I installed (long story) and it had a few gouges and some rust pitting. I gave it a few extra coats of POR15, then went back while it was tacky and applied a coat of POR Patch. Sanded it smooth after it set up, then primed with self etching primer (I used their brand), a few coats of Tie Coat, sanded smooth, then a couple of coates of sandable hi-build and then color coat. Got a nice glossy bumper out of the deal, and you can't even tell where the rust pits were (or the gouge for that matter).

Por15 has nothing in it to reprevent UV rays from "fading" it. However I have used it anywhere that is not in the sunlight and it does very very well.

That is true. I had topcoated my bumpers with Chassis Coat black, which is supposed to be UV resistant, but it still got a "chalky" look to it. I just sanded it smooth, primed, and re-topcoated with regular paint.

I had issues with bondo over my POR-15... it bubbled up...I didnt wait long enough and it was a bit chilly...

POR-15 recommends you use their products....

I think I am going to clean the metal with POR'S Metal Clean and coat the outside welded area on the back panel & inside the drip rail with POR-15, let it set for a week then seam seal the drip rail and skim coat the back panel with my regular plastic filler, prime & paint over it with the urethane single stage I bought a few months ago.

2k primer lifted in a few spots even though prepped with 180.I only would use por in non "paint" areas like floor,int.firewall,inside doors,trunks,chassis,window channels,ECT.I have seen someone use por as resin to fiberglass a 1.5in rust hole!!

I can only imagine the POR was still curing,i.e giving off gasses.
I've painted over bondo with no ill effects.
I agree with carpoor though, I would save the POR for non-topcoat situations. POR recommend their 'tie coat' (They would!)
I certainly wouldn't use it in exposed bodywork areas and try to overpaint.

you mentioned your welds being messy, are you using flux cored wire? flux cored wire is usaully not allowed in the body shop business because of the contaminants(flux residue)creating a rust through problem because of the acids in the flux and the possibility of an adverse reaction to any fillers you may use.If you are using gas as a shielding agent, you may not have your regulator set right(enough flow to shield the weld), your material being welded may not be clean enough(rusty metal will pop and sputter and leave a huge mess,blowout and look crappy)I also use a piece of copper or brass behind the weld as a backer for the hole. the weld does not stick to the brass or copper and it allows you to fill the hole without it blowing out. something to think about

Its a cheap flux core welder, so its just typical flux core splatter.

I have some patches I welded on my fenders well over a year ago and have left them bare metal in my garage and there are no signs at all of any rust forming on either side of the welds.
I think as long as I clean the metal good & coat with POR-15 it will be OK.

POR 15 is some good stuff. I have been using it on the inside on the cab where some rust was below the rear window. I welded new metal in and on the inside I used POR 15 on the inside and no rust has returned. That was 2 years ago and the cab has been sitting outside in the weather waiting for me finish...

Good Luck

Sean

Try using 3M Panel Adhesive Part#8115 Heat lightly with heat & it will flow into pinholes as it cures

I would try to get the pinholes corrected with the weld. Either you do not have enough gas, or you are not using flux core wire, or you have other contaminants causing pin holes

for some minor blemishes, I have used lead in the past as well as filler over POR15. I would not recommend the lead to a novice.

POR15 is a good product, not as good as all the hype, however better than most I have tried. It does need to be top coated.

Alan-

Have you considered something like Fasteel? It's that 2k putty stuff that you knead to activate and then just press it in. The beauty of the stuff is that's its readily available at a FLAPS.

I don't know how porous it is though.