Navy Ship Aluminum-Steel Transition Joints - Galvanic Corrosion

1980s David Taylor work on waffle-steel cellular superstructure to escape aluminum-fire problem. Steel-aluminum transition joint mentioned but not developed.

I was around at David Taylor in the 1980s when they were trying to go from aluminum superstructures to waffle steel construction — cellular superstructure that would be lightweight. The problem with steel is it's heavy, and it corrodes. The Navy uses a steel-aluminum transition joint. All this stuff is part of why we get to study welding metallurgy.

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Three-ply explosive-bonded transition joint allowing fusion welding of an aluminum superstructure to a steel hull. Galvanic corrosion in seawater is the persistent problem; the Sheffield case (§4.p2) is the proposed consequence.

Another application is to make plates that bond aluminum and steel together. [Tom shows a three-ply transition joint.] These are transition joints where you slammed aluminum against steel in an explosive bonding operation, then cut it up. This is what the Navy does for all the superstructures on their ships. The hull of the ship is made of steel because it needs to be inexpensive and have good capability against people shooting at it. The superstructure — the top of the ship — needs to be lightweight, or the ship will tip over in a storm. So they have a steel base plate and put one of these transition joints in. This one happens to be a three-ply: carbon steel to aluminum, with one of these transition plugs.

Student-recovered piece from a Navy ship's head, where the steel-aluminum transition joint at the bulkhead had corroded clean through. Held by Harold Larson; polished sample shows the corrosion path. The breeze through the wall is what alerted the student.

I should have gotten it from Harold Larson, but he won't be in until tomorrow. One of the students here had recovered a piece from one of these ships where you have the corroded holes through the wall. He was in the head — the toilet on the ship — and he noticed a breeze coming through the wall. On the other side was steam from the engine room, and the breeze was coming through because it had completely corroded away. It was at a steel-aluminum transition joint where there's tremendous corrosion. He just picked this up out of the scrap yard and took it home. So Harold Larson probably still has it. I have a little piece that we polished and you can see the corrosion — it just corroded through the steel like mad.