Aluminum Corrosion

[DFreedom]

I am in the process of rebuilding my aluminum I-beam trailer, new hubs, springs, shackles, axle bolts, plates, bunks and bunk supports. It should be like new when I finish. When I removed the galvanized (now rusty) bunk supports, there was what appeared to be crusted on salt deposits between the supports and the square aluminum tubing. Upon cleaning this off with a wire brush, it appears that the aluminum has corroded (it s pitted). Is this normal, is it a reaction between the alum/galv? It is not close to going through the tube but, what should I do to these spots, and is this something I can inhibit when putting new supports on? Last question, this is a flats boat so the boat sits entirely on the bunks, not on keel rollers. Would it make a big difference if I moved the bunks out/in a few inches to avoid these "corroded" areas? Thanks for any/all input.

[Rival1]

If something that holds moisture is laid on Aluminum it will corrode. It is called Poultice corrosion. If there was another metal touching that spot it was galvanic corrosion. If the corrosion is mostly cosmetic it could be cleaned and filled with epoxy.

[165Striper]

I wouldn't move the bunks. It does, by your description, sound like galvanic corrosion due to dissimilar metals. The best thing would be to separate the metals so that they do not touch. I am certainly no expert on setting up trailers but I would talk to a trailer supply store and ask what to use to separate the metals. It seems that I have heard of a type of "grease" or something that can be used or maybe a thin piece of Teflon.

[welder]

You need to isolate the two Alloys .

[Beaubeau]

It might be easier to add some zinc anodes to take hit instead of the trailer.

[welder]

The zincs on the trailer might mot do much as the trailer is not in the water .

The water is standing between the to Alloys while in the driveway and making the battery there.

The above poster needs to separate the dissimilar metals and the problem will be gone.

[165Striper]

The zincs on the trailer might mot do much as the trailer is not in the water .

The water is standing between the to Alloys while in the driveway and making the battery there.

The above poster needs to separate the dissimilar metals and the problem will be gone.

What do you think would be the best way for the OP to separate the metals? Since it is the bunk brackets, the connection would need to stay strong. I would be concerned that a plastic would give and allow the bunk brackets to move. I have a glass boat and a galvanized trailer, so I don't generally have these issues but I am certain there has to be a relatively simple solution.

[welder]

We need to put something on those parts that will help keep the water out .

Bioshield

Grease

WD40

Or something to that effect .

[bly]

We need to put something on those parts that will help keep the water out .

Bioshield

Grease

WD40

Or something to that effect .

I use to work in oil refineries, When bolting up valves or special fittings of differnt metals we would use what is called a Dialectric washer kit. It consisted of plastic washers and sleves that Issolated the two types of metal. along with a Issolating gasket set. For doing a trailer I would atleast grease everything as welder said!