The Stovebolt Site Forums The Shop Area Paint and Body Shop Preparation and paint advice needed

Hey all,

I need a little guidance here...

I am working on the stake pockets of my 1942 dump truck. The old ones were badly corroded as they tend to trap moisture/debris. It also appears as though originally some of the blind areas were never painted/coated before they were spot welded. Like many restorers, I want this old girl to last another 75 years after my work is done.

I figure a picture is worth a thousand words so here goes:

[img]http://www.surfacezero.com/g503/data/3285/IMG_28024.JPG[/img]
This is a reproduction stake pocket that I am going to plug weld after I get repair patches installed on the original bed.

[img]http://www.surfacezero.com/g503/data/3285/IMG_28005.JPG[/img]
This is an image of the cross section of the new pocket. Note the channel within the hat channel that will not be able to be painted after plug welding

[img]http://www.surfacezero.com/g503/data/3285/IMG_28015.JPG[/img]
This image shows the interior channel a little better. The area between the inner channel and the bed side will be very difficult to coat after the pocket is installed.

So do you think I should paint the entire blind section areas with 1)weld through coating, 2)regular enamel primer both before assembly, or 3)douse the pockets with ospho after assembly?

I look forward to your thoughts.

Paul

That "blind" area is a prime candidate for practicing patch panel welding, imo, but I've left/welded over far worse. If the rust hole is staying, I'd just prime it & weld the replacement pocket over wet primer- after using some sort of acid wash & thoroughly neutralizing it. The replacement piece almost looks like a perfect fit. Are you cutting out a square or rectangle spot for it to be welded in?

For longevity of 75 years, or so, I like 2 part epoxy primer. I don't know which rust converters are "ok" for epoxy primer because I've only used the 2 part primer on new and/or media-blasted metal.

Brad

I would media blast the pieces using 80 grit garnet media before welding together, then after doing those stitch welds to hold the channel, media blast the welds and epoxy everything. Use brush, roller, sponge, etc, whatever will do the job. Clean the spots where you plan to plug weld and touch up the best you can once welded in place.

Good to hear from you Brad, haven't "seen" you around much lately. Yes the rust out sections will be replaced with new metal.

Robert, I am trying to use up paint/materials with this project so I will be using red alkyd primer. I would assume that your procedure would be the same, but with a lesser quality coating than epoxy?

As a general question, what are your thoughts about weld through primers when plug welding lap joints?

Thanks for your input gentlemen.

Paul

Paul, sorry I missed your question.

If your red alkyd primer is compatible with what you plan for the top coat, then by all means rock on!

Weld through primers for the most part (there are always exceptions..) are a misnomer in that you don't weld through the paint. Just like any other paint in the direct vicinity of the extreme heat from welding, the paint is going to liquefy and outgas, in most cases causing the dreaded volcano or ballooning you see of a porous weld. Just like any other paint, the weld through should be removed from the immediate weld area.

Secondly, I read an automotive restoration publication many years back that did a comparison testing between epoxy and weld through primer. Their results had the epoxy showing better long term protection. Epoxy is the mixing of separate components that cross link. In my mind (insert jokes here) there is no way I see something non-catalyzed coming out of a spray can (the form of most weld throughs) as a better product than epoxy.. All that aside, ANYTHING is better than the bare steel most of these hidden areas had from the factory. For the most part I'll spray/brush/roll epoxy onto a part and after curing clear off the paint from the plug weld hole areas to eliminate the issue with porous welds. If you've had a chance to look at the recent updates on the Biederman fenders we've been repairing in the shop (link in my signature) we actually used NO primer between the lapped seam so there would be less chance of degradation of the plug welds, and then after any grinding etc was done, we used a brush to apply some SPI epoxy. By dragging the brush across the flange edge, it wicked the paint between the seam of the two panels. When we had paint coming out the other side, we should have good coverage. Epoxy is going to get blocked out regardless, our intent here is to prolong having to make that same repair again any time soon. Granted, this may not work in all situations, especially when the part isn't portable like the fender we did. So use the process that works best for the area you're working on.

Thanks for your input Robert, no worry about the time lag as everything seems to take more time than expected. Work takes up too much time! I cut out the rusted portions on the truck body and welded in new 14 ga plate patches. After welding, I painted all of the surfaces on the stake pockets/body and plug welded some of them back onto the truck body. Aside from the paint burning near the plug welds, all looks good. Just need some time to finish the other side. When originally installed, it doesn't appear as though the blind portions of the pockets were ever painted so my "repair" is still a little better than when she rolled off the assembly line.

Paul