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Frame stiffener prep question

J

Jhumphrey

NAXJA Forum User
Location
Nashville, TN
I'm getting ready to purchase middle stiffeners from HD. I want to make sure that I have my prep right, so when I grind down the undercoating (bare metal) for the rosette welds, do I use weld through primer?
 
I figured that was correct, I just wanted to make sure. Ive looked over a few write ups and they dont show any priming before they weld. My plan is to go over the stiffeners (and plugs, obviously) with undercoating once I am done to make everything "neat".
 
I despise weld thru primer, and refuse to use it. It's fine if you are welding 1/4 thick structural steel with arc welding, but with all the variables involved here, adding one more layer isn't worth it to me.
 
I didnt use any on my ruffstuff stiffeners...
 
I've read that SEM or 3M is the stuff to use. I was just wondering if its advisable to use or not. I know normally that you would use that on auto applications, but haven't read anyone using it on their stiffener project. As I said, I planned to grind down the undercoat, go to bare metal, and then plug weld. Once that was done, I was going to undercoat over the stiffeners (the stiffeners are bare metal).

I've heard that some don't like weld through primers. Others say its an essential part to prevent rust. Since this is a unibody application, the room for error on this is zero.
 
xcm said:
I despise weld thru primer, and refuse to use it.
Click to expand...

This. Its absolutely terrible trying to weld it.



When I did all my stiffeners, I clean the rails down to bare metal and the painted them with a good regular primer. Mocked the stiffener in place and traced a circle were the rosettes were. Pulled the stiffener out of the way and wire wheeled just the marked spots. I also primered the inside of the stiffener itself before welding them on.
 
I will be using a MIG welder. I'm not very experienced with welding at all, but can't find anyone local to help me out, so I have to do it. I plan to practice some beforehand on scrap before I do the job.

I planned to do like Fox and test fit the stiffener, then wire wheel the circle for the rosette. So it's looking like I need to remove undercoat, prime with weld through, trace/wheel, then actually plug weld. After that, I'll spray undercoating as my last step. Thats after I grind the plug welds flat.

Sound about right?

Oh, and is one can enough or do I need 2?
 
Last edited:
No need to trace if you use the weld through,
that is for regular primer.

After they are weldes, you might prime and paint using regular stuff before the underbody coating. I dunno how porous that stuff is
 
Ive never had a problem welding thin metal with primer on it before. The unibody frame rails are thin enough that you will have no problem getting heat and good penetration to them. Once you start arcing to the stiffener the weld will burn right through the primer. At least with my experience. If i were welding something that was more important like a cage or suspension links where i absolutely needed to make sure the welds penetrate then no i would not paint with primer before welding. Stiffeners arent as crucial as most make them out to be. They are important and must be installed correctly but it isnt the end of the world if not every little rosette weld is perfect. Just make sure You have a good weldi g jacket and can find a comfortable position to wled in. Being upside down getting burnt sucks and stiffeners are a p.i.t.a.
 
All good info, I have always just removed all the under coating welded the stiffeners on and re-undercoated. The stiffeners will outlast the rest of the rig.

It's also a good idea to wear earplugs while welding the underside of things, nothing much worse than catching a piece of weld slag in the ear.
 
I sanded it down and just primed the back of the frame stiffeners and had no issue but remember the unibody is galvanized so if you dont prep it correct it will fight you a little. I as well used a mig welder and it came out awesome and hd offroad makes amazing stiffeners fit was spot on
 
Also happy with HD offroad.
mine needed modding to fit, but I was told they changed.the design to meet the issues I raised to them
cant ask for much more of a company
 
I didn't use weld through primer... but I live in socal, we don't get much rust here.

I did use a heavy dude caulking to seal the gaps in the top, then painted everything with a rattle can.
 
I live in TN, which at this point has become an extension of Seattle when it comes to rain. Plus, we have a lot of mud. While rusting isnt as predominant here as, say, New England, its still something I have to consider.

Originally I thought if I were to grind down the undercoating, weld the stiffeners on, and then cover all that back up with undercoating, I'd be fine. Then I had read somewhere that you should use weld through on any auto body part, especially if its "outside" to prevent rust.

So far it seems like a mixed bag on whos primed and who hasnt. I guess that when I order the undercoating, Ill order a can of weld through to be safe. I read that "regular" primer may or may not work and I also read that using regular primer gave off fumes. I cant remember where I read that though.
 
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