TOPIC: Chemistry of Galvanic Corrosion

I can remember from my high school chemistry the "why" of galvanic corrosion. What I don't understand are the results and how best to deal with them.

Everyone here, I'll bet, is familiar with the White powdery substance which results from galvanic corrosion. Chiefly, between Aluminum and Stainless Steel. I am dealing with that plus a very similar powder binding up Brass and Aluminum.

What will react with this stuff and make it go away? I am thinking if it is a base, I should attack it with a mild acid (to start with) such as vinegar. I can advance step by step to Hydrofluoric acid.

If it is an acidic substance, I will start with baking soda and work my way upscale from there.

Any Chemists out there?

Well, long ago my BS was in Chemistry. Add an MBA and I am armed and dangerous. My chemistry degree long ago was convoluted to radiochemistry, most recently applied to the problems in Japan.

First and foremost, galvanic corrosion is not about acids and bases. Rather, it is about the flow of electric charge. Dissimilar metals will create current. When a current is established it tends to eat the softest metal. Hence the need for sacrificial zinc anodes, and more importantly, really good grounds.

its a base , use vinegar, or muriatic acid for the real bad jobs , be certain to rinse well

Well, there. Now that's an answer to the question! And I love the Avatar, too. As an ex-Fire Marshal, I cannot say enough for Master Jim!

All I want to know is how to dissolve that white powder. In a few days, when the windshield folks call and say, "Your glass is ready", I should have removed the two pieces of the Brass corner brace (or connector) from the Aluminum window frame and fused them back together. If I can apply some sort of substance which will soften or dissolve the white sh . . . er . . . stuff which is welding them together, it will be great.

Thanx!

Well, I'm not a chemist, and I don't play one on TV, but I can tell you that the best stuff I've ever run into for freeing stuck parts is something called "Free All". Not sure the chemical process, but it works great on galvanic corrosion. May have to get it at a HVAC supply store.

I found it on the web nd I'll look for it at the store. My favorite in the past has been KRoil, but it's not really something which will react with, and change the nature of the corrosion.

LOL...guess I should read the string more carefully! It was not the process you were asking about, but dealing with the result....sorry!

The title might have been misleading - my bad.

In either case, I got the little *&^% apart! I tried penetrating oil, I tried LPS cleaner, I tried KRoil, BreakFree, a Propane torch and finally, a Dremel. I sliced off an inner flange of the Aluminum frame, which freed up the Brass insert on two sides. I still had to ease it out with a screwdriver and a hammer.

The Brass was welded to the Aluminum with, not only the normal White corrosion, but a layer of Green. The Copper in the Brass must have added it's chemistry to the mix.

The Brass polished up fairly easily on the wire wheel, but the corrosion in the Aluminum window frame is going to take more - possibly a whatdoyacallit? Those grinding thingies for an electric drill. Not abrasive, but all steel with Carbide teeth. One of those. Having a senior moment, here.

I'll need to use the same method on the half that is in the other part of the Aluminum frame still hinged to the boat. I can't do any hammering on that part or I'll rip the hinge, etc. It's okay to remove that flange, the Brass corner insert will be held in with several screws.

But, now my Moto-tool decided to die on me. I took it apart, the brushes are good, the wires look fine, I cleaned the inside of the variable-speed switch, NADA. It's 15 or 20 years old. Time for a new one, I guess and file the old one with it's predecessor on the "someday I'll fix these" shelf.