Metal finishing Q&As since 1989

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Dissimilar metals attack hurricane shutter industry

I recently founded a hurricane shutter manufacturing company on the East coast of Central/North Florida. For years I have seen the effects of galvanic corrosion on aluminum hurricane shutters up and down the coast. Seeing very little being done in my industry, I want to do something to mitigate this problem. I have begun by replacing some stainless steel fasteners at aluminum to aluminum connections with aluminum rivets. Some stainless fasteners however cannot be replaced. I have found a nylon washer (in theory) works well, but I know that the screw shaft is still contacting the aluminum. Do you know if there is a washer with an integral sleeve available on the market. And do you have any other thoughts which I could use to improve my products.

Mike O'Connell
product designer - Ormond Beach, Florida, USA
January 25, 2009

My initial thought was wall plugs... that's what we call them in the UK. You make a hole in the brickwork insert the wall plug then screw into that. They come in various sizes and length's... it may require one inserted from each side. Just a thought to get things moving.

Terry Hickling
Birmingham, United Kingdom
January 27, 2009

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First of two simultaneous responses --

McMaster-Carr sells something like this. They call it a shoulder spacer with flange. It is on page 3206 of the catalog. Nylon and PTFE I think would work.

Jon Culp
- West Chester, Pennsylvania, USA
January 28, 2009

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Second of two simultaneous responses --

Hi Mike,

When I had a corrosion problem like yours, I used to use a mild steel bolt with a stainless washer BUT I coated the threads with graphite to occlude corrosion.

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).
January 28, 2009

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Hi Mike,
Instead of trying to insulate the fastener from the aluminum, I would try using a dip/spin finish on the fastener. There are finishes out there that have very good bi-metallic corrosion resistance when mated to aluminum.

David J. Wolf
Medina, Ohio
March 11, 2009