There is rust where my running boards meet the rear fenders on my truck. It has been 16 years since my truck was fixed up and painted. I got the rear fender patches from Mid-Fifty. I stopped by the body shop yesterday to ask questions about when he can fix my truck.

I asked him if he butt welds or lap welds the pieces. He showed me a crimping tool he has that is run by his compressed air system. He crimped two pieces of scrap metal and showed me how they fit together. I asked about moisture getting between the two pieces. He said if you seal it in back it should not get moisture in the seam. I told him the patch panels are 16 guage so maybe they can be butt welded.

This is the same guy that did my truck in 1999. He did a great job on making a rust bucket into a nice truck. But I didn't think my fenders should rust out so soon. The fenders i used needed to be patched athe same spot. I don't remember ifni got fender patches or he made his own. But it has been 16 years What do you think?

 

I am by far, no expert on the subject. I figure a perfect butt weld, sealed and painted correctly would last as long as the original. This depending on quality of repair panel and care taken of the vehicle. I would think a lap joint could be a bit more susceptible to moisture intrusion but if sealed correctly should last more than 16 years. We must admit, the double stack metal in that area is not Ford's best idea, a dirt and moisture trap.
Question: Is the truck garaged and is it ever put away wet?
Do you drive it when there is salt on the roads?

 

16 years is a long time ,considering where you drive ,maybe salty roads. Butt welds don't have anywhere to hold water whereas lap welds do. The area inside the fenders are prone to moisture. Years ago I had rocker panels replaced in an old truck at a body shop an about 5 years later they rotted out again. The panels were new from lmc . We have humid weather here in Texas. Years later now I do all my own work so I'll know how it's repaired. Sorry your truck needs work, still looks good in the pictures though.

 

If he intends to use a flange then structural adhesive is the best way to go...strong as weld, no warpage, and the whole flange/seam is filled with adhesive so that no moisture can ever get between the two sections of metal.

 

Charlie, I know you are a big fan of structural adhesive. I also am using them more and more. My questions in the back of my mind are, do these adhesives have any kind of lifespan? Do they break down over time? Any affect from heat and cold cycles?
Just curious, but if you have any info or links to it I'd appreciate it.

 

I demonstrated to my rust repair workshop students this past weekend that no matter how much effort you do, just by the nature of how the metal reacts to the welding heat you will get shrinkage along a weld seam, be it a butt seam or a lapped seam. That shrinkage (sinking of the seam line) can be as much as 1/4" along a butt seam welded with overlapping spot welds and allowing cooling in between, the method I advocate. to as much as 1/2" along a lap seam with a continuous weld bead with no regard for heat control. I taught them how, with careful hammer and dolly work, that shrinkage could be removed to the point of only requiring a very light (< 1/32" or less) skim coat of surfacer putty before ready for paint. It could be finished to needing no filler with more work time. A lap weld because it is two layers of metal thick cannot be hammer stretched back to the original surface "fair line" and must therefore be covered with a thick application of bondo over a wide swath. The double thickness along the seam will not expand and contract at the same rate as the surrounding metal which can also produce "seam ghosting". The sunken seam if under the inside doubler will not allow the doubler to fit tight against the skin, making it a larger moisture and dirt trap.
My answer is that the proper way to do the repair is by butt welding, hammer stretching and truing of the resulting seam followed by replacement of what I'm sure is a rusted out doubler panel. (I suggest reading thru my rust repair tutorial) The doubler and inside of the fender can be given a coat of weld thru primer before the doubler is plug welded in place, or a slightly thinned application of Rust Encapsulator (available from Eastwood) or POR15 run in between. Finally I would seal the edges of the doubler with a wipe of flexible seam sealer all along the edges.
IMHO flanging and lapping a seam, unless it was done that way at the factory is the "quick and dirty" method of rust repair, and is likely to cause problems down the road. A butt welded and finished seam should last as long as the surrounding metal.

 

Scott...3M has two versions of their panel adhesive; 8115 and 8116. One, 08116, has the endorsement of the big 3 GM/Ford/Chrysler...the other is endorsed by Ford and the foreign manufacturers. I don't know what the differences are between them, I have used them both and can see no difference between them. 3M Panel Bonding Adhesive 08116. As for durability, these adhesives have been in use for decades...I first became aware of them being used in the Long Beach port of entry where Datsun and Toyota were bonding mini truck beds with the adhesive. I have never seen a bond fail that was made correctly. Poor abrasion of the bonded areas or debris will cause a failure but I have never seen the adhesive itself fail...and I have gone way beyond the limits of its recommended usage more than once with great results. Ford bonds their FG truck bed sides onto the metal box with this adhesive and many other manufacturers use it for various other jobs. Some of the foreign car makers like Lotus assemble virtually the whole car with structural adhesive. There is a great video series on the History channel called "Ultimate Factories" where they have toured Ferrari, GM Corvette, and other assembly plants...if you get a chance check these out, you will see just how much structural adhesives are in use in today's high-end automobiles. Bottom line, I don't think that these manufacturers would be using structural adhesives if they had a life-span issue or in any way a hot/cold issue since safety is of upmost importance in the auto market today.

 

I agree with Charlie with the exception that neither the adhesive manufacturer nor the OEM manufacturers recommend using panel adhesives for joining two panels and covering the resulting seam with body filler such as might be done in doing rust repair. If you read the factory instructions they state that the entire panel must be replaced. That puts the seams and adhesive line along wrapped/flanged edges or possibly under a strip of trim. If two panels are joined where the seam cannot be hidden, the two panels join along a flange on each and the resulting seam is filled with seam sealer rather than body filler (the depressed lines often referred to as "body lines". Body filler is not used over the glued joints.

 

I am not sure where you read that about not using body filler over structural adhesives but I do it all the time without issue. One thing that is recommended is that if you do have a bonded seam that will be visible/painted, that you do sand back the adhesive and cover it with body filler. Here is a link to a Kevin Tetz video ( ) that covers the pros and cons of welding vs bonding. In this video Tetz recommends filler over adhesive, that is where I got the idea and so far it has worked just fine.

 

true, but it seems, more and more, that quick assembly and cost reduction rules over all. I believe BMW, for one, forgot about quality and durability in their cars, beyond the warranty period, despite longevity being a selling point that is of import to some of us buyers.

My fabulous fabricator does butt welds on such areas, for minimal body filler and a flush, finished surface, fore and aft.

 

That is true...but it does not mean that quality or durability must suffer as a result. That said, we have become a "throw away" society that values new style over quality and durability. Makes you wonder what our grandchildren will say when they are the ones resurrecting the "classics" that are currently coming off the assembly lines.

 

I just don't see anyone on a major scale 50 years from now wanting to restore a Prius in the same manner we look at muscle cars, or the previous generations honored the 50's and earlier cars. The culture has changed and the automobile isn't as revered as it once was. The car has become more of an 'a to b' mode of transportation, rather than something special the neighbors all gathered to look at when a new car came home.

 

Great discussion but I'm not sure there was a general concensous! Adhesive is tempting for us welding challenged but at what risk? No one wants to revisit repairs.

 

There will never be a "general consensus" because there are always those, not unlike the Spaniards waving their fists from the beach at Christopher Columbus as he sailed into the horizon, yelling out "you are going to die you fool!". I am a degreed engineer and consider myself to be an "early adopter", but in this case that title is no longer appropriate...the train has already left the station. As long as the discussion is kept at the "armchair quarterback" level there will be doubters, all I can offer is that if you really want a better way to do many bonding tasks then you owe it to yourself to try the adhesives and make your own objective judgment on how well it works for you.


In all the posts I have made about structural adhesives I have yet to have one negative response from someone who has actually used the product and has spoken with a voice of experience.

 

My body man says the adhesives are expensive and welding parts is cheaper.