I have corrosion under the door kick and scuff plate areas on a car I'm preserving.  Recently I've been reading articles on metal bonding vs welding and was wondering if anyone has tried fabing up a sheet metal piece to fit under the kick plate and use a structural bonding adhesive as opposed to welding it to the top of the door sill.  In my case the rocker panels look good inside and out as the result of being rust proofed when new.  The rust appears to be a top down problem at the pinch weld and under the door weather seal/kick/scuff plates only.

I'm not saying the metal bonding glues aren't useful in certain circumstances but if you have rust then no amount of patching with glue or welding is going to help until you remove the rust completely.

Personally, I would always trust a true weld over a surface adhesion.

Butt welding is best for patch panels like what you are describing. 

 

Structural adhesive bonding is actually much stronger and consistent than spot welds, but it should only be used on fresh clean metal. A lot of high-end luxury cars glue panels together these days. 

From what I've read a clean bonding surface would be an issue although acrylics seem to be more forgiving.  I've seen video of panel bonding where a thin bead of adhesive is used on the lip of the part but that's not what I'm thinking about.  When I go over the possibilities there are three choices.  One, I can clean up the area and patch it with body putty, put the kick plate back on and call it a day, not good.  Or...two...I cut out and re-weld both rocker panels, a very big job which might happen eventually anyway. Or...three...I fab up a cover piece the same size and shape as the kick plate from 22 gauge steel and bond it to the sill and place the kick plate over that.  75% of the surface would be bonded to good metal and the adhesive would encapsulate the remaining corrosion.  When you think about it what's the worst that could happen if the patch fails...it's back to option two.  But maybe with the right adhesive the repair holds, the sill is strengthened and the surface rust is stopped.  Think of the possibilities....

Its a mistake to assume rust remains "encapsulated."   It doesn't.  Rust never sleeps (to quote Neil Young).

The rocker panels have 2" diameter or so holes all down the interior sides. So they have very good access to atmospheric humidity. You may slow the rust, but its still gonna rust from humidity. The job only gets bigger the longer you let rust run... my 2 cents

C

Good point...on cars that rusted from inside the rocker panel.  As luck would have it this car received a Ziebart treatment when new and the corrosion is external from moisture getting under the weather seal and kick plate.  In my original post I asked if anyone has used structural adhesive and it looks like the answer is no.  I guess the only way to find out if it will work is to try it and see what happens.   

How bad is it?  You might just be in the typical rust-removal and seal-coating regime.  The typical POR-15 or Eastwood treatment.

 

http://www.eastwood.com/paints/rust-solutions.html?SRCCODE=GA200110&device=c&matchtype=b&network=g&creative=56087209260&gclid=CLGNyOuXqMICFUeEfgod9hcA6A

I've used POR-15 and it works fine, but because there are spots that are rusted through the idea is to bond a doubler under the kick plate to seal and strengthen the rocker panel.  The plan is to fab a 30" long piece by bending two 90's it to match the shape of the top surface of the rocker panel, bond it with structural adhesive and cover it with the kick panel.