"Don White" wrote in message
...
Gene Kearns wrote:
On Thu, 20 Apr 2006 15:56:31 GMT, Don White
wrote:


Here on the salt water we only use stainless steel or aluminum backing
plates. Why ask for trouble?


Good advice. Also, I *really* don't recommend aluminum and steel
combinations.... dissimilar metal corrosion will cause way more
trouble than you want to put up with.


Unless you have a way to isolate them from each other.
I've used 3M4200, liquid tape, gaskets made of plastic etc to make sure
the different metals don't touch each other. If you've ever drilled or
cut 1/8th thick ss plate, you know why I changed to 1/4" aluminum backing
plates.


And you want 5000 series aluminum. 5086 probably the best for most jobs
where salt water is contacted. 6061 is a tougher alloy. The 5000 is very
low copper content.