Polyester Resin and Aluminum contact?

[reelfishin]

I was talking to someone today who works with fiberglass and boats for a living. I was told to be careful about using polyester resin to water proof or to laminate anything that will contact aluminum? I was told that it would cause corrosion anyplace where it may come in contact with the aluminum hull?
Has anyone heard this before? If it's true, does it mean that its only corrosive while it's curing or after the fact as well? I have seen people laminate several layers of plywood to make up the transom reinforcement wood on aluminum boats and never really gave it any thought. I used epoxy on all of mine, but only because I already had it here and have a good source for it.
I have also used Bondo on aluminum body panels with no problems, but I have always prepped the panel with an etching primer first.
I also heard the same thing from a body man once, but never gave it much thought or put much weight on his opinion, this guy repairs boat hulls for a living and has an engineering degree. What has me puzzled is that some polyester resins use aluminum as a reinforcement, although not for the boat industry, they do exist.

What I am thinking is that if polyester resin or filler was used on aluminum without the proper prep work, it may allow water to penetrate the joint of patch, thus causing corrosion?

Does polyester resin corrode aluminum? Has anyone ever heard of this before?

 

[Ezrider_92356]

Re: Polyester Resin and Aluminum contact?

iv never heard of it, dosent mean it might not be true but i have heard that presure treated lumber will react with alluminum

 

[tashasdaddy]

Re: Polyester Resin and Aluminum contact?

i haven't heard it either, but PT will definately react with most metals.

 

[reelfishin]

Re: Polyester Resin and Aluminum contact?

I have seen pressure treated wood eat at aluminum, but never polyester resin.
What gets me is that two people that have been in the business for years both agreed to this, like it was a well known fact.
I wouldn't use polyester resin in most cases anyway, I prefer epoxy. I think maybe someone slapped some fiberglass resin on a bare aluminum hull and it fell off years later revealing corrosion, most likely the result of poor prep work and salt intrusion. I can't picture there being any corrosive chemicals in cured resin that will harm aluminum. I can picture a bad repair not adhering to un-prepped aluminum allowing saltwater to get between the resin and aluminum and corroding, but not a contact problem where chemicals in the resin attach the aluminum hull.

 

[ondarvr]

Re: Polyester Resin and Aluminum contact?

I'll need to ask more about that one.

It could be corrosive because it contains trace amounts of metals like copper and others, plus catayst is an oxidizer, so in a liquid state it will react with aluminum. But I have used it on aluminum and not had any issues. My current aluminum jet boat has a honeycomb floor overlayed with glass that runs up the inside of the hull several inches, it's held up for over 6 years of hard use with no delamination or corrosion that I can see. This boat only gets used in fresh water. I don't recommend using polyester resin on aluminum for any structural purposes though, it just doesn't bond that well.

I've read about bonding issues with aluminum for marine use though. it appears that while many things will stick to aluminum very well, over time oxidation may occur bewteen the aluminum and whatever "glue" is used, thus weakening the bond. This seems to have more to do with the aluminum and how it ages, than what is used to bond it, but I'm sure some products work much better than others.