Dissimilar Metal Corrosion

[JIM Bowers]

In the process of repairing the rotten floor and corroded metal at the rear of my 25 Trade wind I found a 42 inch long strip of steel riveted to the inside of the rear skin at the floor, were it has caused considerable corrosion. It is placed so as to fit under the wood floor panel.
Any idea why Airstream would have installed the steel, it is about 14 gage thick, and what would be wrong with replacing it with 2024 of the same thickness.
Your comments will be appreciated
Jim

[dwightdi]

It depends on what the steel was in there to accomplish. If it was a stiffener to prevent bending or spreading out a stress then you would want to use an aluminum piece that would have the same resistance to bending. Aluminum has a mending modulus one third that of steel. Therefore you would have to use a thicker piece of aluminum. Since stiffness goes by the cube of thickness, you would have to use a piece of aluminum that was 1.4 time the thickness of the steel piece to get equal function. Make sure you do not use steel bolts to attach it or you will have the same corrosion problem from the bolts. I use plastic washers under stainless steel fasteners when I do something like this.