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Attaching Sheet Aluminum Patch Panel Over Steel Panel


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Posted

I have a dent in a trailer and I've had a piece of sheet aluminum made to screw onto the sheet metal and act as a new panel.  Everythings cut and holes drilled and I wanted to know with regards to heat, the sun and warpage,  assuming that both panels are roughly the same temperature,  should I apply the new panel in the cool or the heat?

Posted

Well that's basically all I need to know. Thanks. I just thought that they might expand at different rates and buckle the patch sheet.  It's a good size panel.

Posted

An aluminum patch on steel panel is by its very nature a short lived band-aid as they are dissimilar metals and the galvanic action will promote oxidation.

  • Like 3
Posted

Primer on both metals will not help?

Yes, it will help. If you can isolate the two materials, it will slow or stop galvanic corrosion. Although, your first concern, differential expansion, is still very valid. Depending on the thickness and alloy. The aluminum will expand more than the steel in sunlight or other heat and oil-can/warp/bend depending on how large it is.

Posted

It has been a long while since I applied primer to aluminum..I used zinc chromate primer,(follow the directions for use).

Posted

". . . . the galvanic action will promote oxidation. . . "! Great information, properly used, one could achieve a faux, faux original patina! Got to add this to my notes!

  • Like 1
Posted

Different expansion rates, galvanic reactions. you need a 2k primer for aluminum.

Posted

Well, it's not really a patch.  When in place, it will look like a panel on the trailer.  I had it made at a sheet metal shop.  Whether it will last, or how long, I don't know. I looked online at web sites that gave information about using various metals together,  and aluminum on steel rate a 0-1 with respect to serious reaction.  It's not a car and so I'm not too fussy abut it.  Actually, most of the aluminum panel doesn't even touch the steel due to the gouge/damage in the steel.  The perimeter will be sealed with caulk.  

  • Like 1
Posted

If you are sealing it with caulk then don't screw it down. The caulk will act as an insulator to prevent oxidation, a glue to hold it in place, and as caulk is flexible expansion rates will not matter. Both problems solved. 

  • Like 1
Posted

you need to use alodine, then zinchromate......

I, for one, wouldn't argue with a man who sported a tattoo of an anchor from an early age.. ;)

Posted

Just have to ask:  If this panel was made at a sheet metal shop as you say, why was aluminum used instead of sheet metal?

Posted

Well, because I use this fella quite a bit for other projects where I've always use aluminum like Art Deco furniture and stuff like that.  I like using aluminum and I wanted to cut down on trailer weight.  But I'd go steel if I had it to do over.

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