I’ve found that a 1/4 " beam clamp , yaknow the clamps that hold electrical fixtures to an I beam, make a nifty fish rod holder clamp.
Problem is they are galvanized and the boat is aluminum. There will be a chemical reaction between the galvanized clamp and the aluminum boat. Its obviously easier to remove the galvanize than the aluminum.
So does anyone know of a cheap homespun way to remove the galvanize coating? I’m thinking acid bath here.
Won’t there still be a galvanic reaction between the aluminum and the steel?
How difficult would it be to insulate the clamp from the boat? Say, wrap the target area of the hull with electrical tape and something stronger, such as a rubber or fiber washer under the clamp screw?
Maybe some but I can/will paint the steel.
The reaction with al and galvanized will be severe since it takes moisture to get it started.
Yep. If it were me, I’d coat the clamp with a good electrical varnish, like Isonel and then insert Nomex strips under the pressure points where it’s going to be clamped. That’ll keep the clamp from rusting, too, which it would absolutely do once you strip of the galvanized zinc coating.
Hey Q
any idea how to strip the galvanize?
Couldn’t you just reverse-galvanize it? Put it in an acid bath, connect the anode of a battery or power supply to the galvanized clamp, connect the cathode to a copper rod or tube. If I understand electro-plating correctly, the zinc coating on the clamp should begin to flow through the solution to the cathode, right? After a while, no more galvanized coating.
Not a clue. I know it’s bonded pretty well to the steel by strong electrochemical bonds. It’s a problem for scrap recyclers. Here is a description of a recently-developed process, though I’m not sure how suitable it wold be for you.
Actually galvanized steel is simply covered in zinc. Let the galvized steel sit in acid, prefereable hydrochloric. No need for a current as the zinc will react with the acid to produce hydrogen and zinc chloride. Won’t take long either. Once the bubbling has stopped take it out because the steel will dissolove very slowly.
As for this reaction between steel/zinc and aluminum, I’ve never seen it. Aluminum is a very reactive metal. So reactive in fact that its surface gets coated with aluminum oxide until the oxygen can no longer react with it. In order for the zinc/steel to react with the aluminum something needs to break through that barrier. Acid or base will do it easily, but I’m not sure that neutral water will. I wouldn’t be concerned about it.
Like, say, the contact points of a loaded clamp assembly vibrating and shaking with the motion of a boat?
Since your really set on removing it, try a wire wheel brush. You may wish to dip some or all of it in Plasti Dip. I’ve seen something like it sold in the electrical section of lumber yards to coat the bare wires.
That sounds like abbrasion rather than a galvanic cell. The reaction with atmospheric oxygen is very very fast. I have never seen a galvanic cell with aluminum and don’t beleive you would ever see one in the presence of atmospheric oxygen.
You can probably just use plain old household vinegar, as I discovered by accident when I put dilute vinegar in a galvanized bucket. Worked overnight and took off every bit of galvinization to the water/vinegar line.
I’ve seen rapid galvanic reaction between aluminum and steel (in a marine environment and an inadvisable design) and the result is not pretty. The aluminum essentialy wastes away to nothing while the steel forms a galvanic weld with what is left of the aluminum. And in nature, there is no such thing as “neutral water”; even freshwater is reasonably reactive.
Q.E.D. has it right; electrical varnish and/or some kind of polymer or ceramic isolator is necessary to prevent corrosion due to galvanic reaction between dissimilar metals.
Stranger
I expect you could get it powder coated quite cheaply.
I stand corrrected. In which case I would expect that the reaction would be quite rapid as aluminum really hates to be anything other than +3. I guess the aluminum oxide must be somewhat soluble in water even at neutral pH.
I consider anything with a pH between 6 and 8 to be neutral. I’m not sure what the pH of sea water is but I’m guessing I would consider it neutral. This is not to say that salt water isn’t really corrosive.
According to a quick search, the pH of natural seawater ranges between ~7.5 and 8.4 which is decidedly alkaline.
Most so called galvanized steel these days is merely zinc plated and easily removed with a short soaking in acid. “Line Away” or similar household product containing hydrochloric acid should do the trick. Rinse thoroughly and neutralize any remain aicd with bicarbonate of soda aka baking soda.
dry in oven, and apply a rust primer and paint.
If it is hot dipped galvanized, there is a thick layer of zinc which will take considerably longer to remove.
Hot dipped is considerably cheaper than electro-galvanized, so chances are it’s hot dipped. Still, the soak it in acid (vinegar, muriatic, whathaveyou).
Still, if you’re going to paint the steel to prevent it from rusting, then why not just paint over the galvanized coating? Okay, you mention shock, friction, whatever, so just take a die grinder to the Al-Zn interface area, paint the part the color you want, and be done with it.
Been soaking one of the clamps in vinegar since noon. About half the zinc is in a little pile in the bottom of the quart fruit jar. 
Changed the vinegar and we’ll see what has happened in the morning.
It might make sense to just paint the galvanize coating but now I don’t have to worry about the zinc at all.
I really did consider grinding the coating off but this is so much easier and not at all labor intensive.
I’m guessing the total cost to remove the coating on all 6 pieces to be about $1.75 or whatever the cost of a gallon of cheap vinegar is at walmart.
Thanks all for your input
just
Just another one of those “AH HA!” moments. Amazing the discoveries one makes by accident.