Filler on stainless steel?

[JayJay]

Folks - I've been working (off and on) for the last couple of weeks to repair a tear in my radiator shell ('30). The tear was in the boss that holds the crank cover, and extended up through the flat (painted) portion to the edge. Photo below shows what we started with.

We have welded, filed, rewelded etc. and have a good structure to the repair. But there are a couple of low spots that have appeared during the welding process due to heat warping, and I've tried blending the metal to the point where it's getting pretty thin in places. (BTW, the stainless started out at ~0.030" - essentially, 22 ga.) I'm left with a couple of places in the flat (painted) portion that are a bit low. If this was a carbon steel body panel I would not hesitate to fill with either lead or Bondo prior to painting.

I have no experience with either lead or Bondo on stainless. Do they adhere to stainless, are there special preparations other than the usual roughing up the surface, etc.?

Thanks a million.

JayJay

[jb-ob]

Jay,

I suspect if you primed the stainless first with a good epoxy primer your bondo will adhere fine over the epoxy.

jb

[Pete]

That could be filled with silver solder and re-contoured.
A heat sink would help make it easier.

[BRENT in 10-uh-C]

Originally Posted by Pete

That could be filled with silver solder and re-contoured.
A heat sink would help make it easier.

Yes, as Pete is saying, -this is where silver solder will work well.

IMO the key in any of the fillers that you are asking about is the filler must have a way to mechanically bond/adhere to the stainless. In welding, the filler metal and the parent metal become molten and flow together to make the weldment. In the case of Lead, body fillers, JB Weld type epoxies, etc., we know that filler does not become an integral part of the parent metal, therefore it must have a good mechanical bond to adhere. This is where roughing the parent metal is important as it gives 'teeth' for the filler to adhere too. While I am a strong proponent of epoxy paints to promote adhesion, -this is one area where I would rather have the filler be applied directly to the parent metal instead of the epoxy paint.

[JayJay]

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Thanks all, for this input. I had not thought of silver solder as I was hoping to find a relatively "cold" solution to avoid any more metal movement. But that makes sense. I do have very fine torch tips so I'll think about this, maybe try on the side flange where it won't show first.

JayJay