The Stovebolt Site Forums The Shop Area Paint and Body Shop Welding after POR-15?

I'm not sure if anyone's experienced problems with this?

I recently had reason to grind off some areas of POR-15 to allow me to install my new MII lower suspension arms,there's a support tube and gusset required on the front crossmember.

Despite good clean back with hard and soft grinding discs I just can't get good weld penetration.
By comparison the supplied (untreated)upper shock mounts had great penetration but where they butted onto the chassis the weld looked like chickensh*t....

Does the POR affect the metal this much?
Any advice/suggestions welcome.

What welding process are you using?

While it is true that a clean surface is ideal, Stick (SMAW) or Flux Core (FCAW) can deal with unclean surfaces better than MIG (GMAW).

Be sure to wear a respirator.. fumes coming off the POR is some nasty stuff.

It's straight forward Argon gas/MIG John,like I said the areas that haven't been painted in any way are fine,it's just when I go near areas that had POR on them despite the fact i've ground them to death!
Thanks for the heads up although I'm well aware of the nasties that POR-15 can produce with or without heat...

MIG with shielding gas is probably one of the most finicky in regards to cleanliness.

We used to weld through the varnish/paint that comes on pipe from the mill. When we used Stick and FCAW the welds worked fine, but MIG would look like bird crap.

I'm not condoning doing this, the best practice is good clean base metals. I am just saying what I have personally experienced.

I'd suggest taking a torch and pre-heating the area you are going to weld to 400 F. That should help drive off moisture and contaminates.

Clean metal is CLEAN METAL. Its a prerequisite for welding period. So, what I do in this very situation is sandblast the area. You can get guns that blast local areas well without too much fallout. Or use 36 grit discs until you get to shiny metal. In any case, if its not very shiny metal, you aren't done. John is right of course, its more about metallurgy and whats best practice. Lots of people LOVE POR 15. That's great and all, but its not mainstream, so if there is fallout like this, start with clean metal and now we have come full circle!

Deve I agree in regards to clean... but what criteria is used to determine what "clean" is?

I spent the last decade of my career in the oil and gas industry engineering repairs to pressure vessels. For these vessels the only way to get them "clean" is to steam clean them. The petrochemicals can't be wiped or ground or sandblasted away... steam cleaning is the only proven means to clean the metal in preparation for repair welding.

In the real world the bottom line is different methods must be employed to produce a clean surface, based on what contaminents are present. If the surface isn't clinically clean, a welding process must be used that has suitable flux that provides an acceptable end result. And that process, for welding on a surface with some contaminents, is not MIG welding using solid wire with a shielding gas.

That's great John.. I even agree, but if all you have is a mig as do most of the group here.. you have to go to extreme measures to clean the metal so the mig can weld it. Clean in that case is whatever is clean enough to get your mig to work properly.

I am one of those single machine hobbyists. I have done amazing things with my mig. Things that wouldn't be recommended if you had unlimited resources and had stick, TIG, other methods at your dispose. You are absolutely correct at your higher level of expertise. Remember, anyone using POR15 is a hobbyist, not a seasoned professional restorer with several machines at their dispose (for the most part). So, I fashioned my response to what I feel is the audience. POR15 is really great BTW. nothing wrong with it.. but the pro resto shops do not use it.. they have a defined system that includes epoxy primer, highbuild primer, sealer, base/clear. Since that's not what we are talking about here, my short answer was CLEAN the metal to mig perfection.

Perfection, not sure how we arrive there, that's why I posted...

I don't use POR so I cant say for sure, but when I get things like silicon contamination, oil residue that has soaked into the metal, things that are really almost impossible, I use PPG's DX330 cleaner. Its a Naptha based cleaner that makes it so that paint sticks very well. Maybe after using 34 grit sanding disks and taking off the top metal substrate, then cleaning with a good cleaner? If you don't have DX330, try lacquer thinner to start. All this amounts to is a challenge. You will overcome it.

Given that your weld is working on the new part, it sounds to me that your problem is the inability to direct sufficient current into the frame to get good penetration. It can be difficult to aim the arc exactly where you want it with MIG as compares to stick or TIG. The new part may be hogging all of the current, not allowing the frame to get hot enough to take the weld.
Carl

Thanks for all the input guys,i've taken your advice on board and will try again,i'll keep you posted of the outcome.

I really need to get this done as my truck is my daily driver for the foreseable future....

do you have the welder set for the thickness metal . i found out if welding a piece of 1/8 bracket to a piece of 1/4 plate if i set the welder for 1/4 it welded better

Leonard the bracket and chassis are of similar thickness,i'm calling in a good friend (and welder) to zap these on for me. Might as well eliminate all potential problems (i.e. Me!)

Good call Jock. You don't want to always second guess what might happen if you don't do it right.

If a metal prep phosphoric acid was used, it does make it very difficult to weld the metal, been there done that.

That may well be the problem then, POR-15 'Metal Ready' is basically phosphoric acid.....i've still not got the welding done yet.

Any suggestions as to how you removed the 'contamination' for want of a better word.

Thanks for the heads up.

Fire... it's been used to solve problems since we started standing upright Did you try the torch? If you don't have an oxy-acetylene use a hand held propane torch...

Got 'er done,there was still a fair bit of spattering,it ain't pretty but it'll do,you'd need to be a limbo dancing snake to see it anyway plus it's a driver not a show truck!

Once again thanks for all the input guys.

So what did you end up doing to make it work?

I just persevered with the soft grinding disc,and gave it a good burning with the gas torch,my friend Gerry then welded it (he's more experienced than I),even then it was still spattering a touch.