ESPcat – DIY Galvanizing – A Huge Bang

There was this huge bang and the entire glass apparatus I was using completely disintegrated into a million pieces. There were tiny bits of glass everywhere. Sulphuric acid too! Fortunately neither of those went into my eyes. Those were the days! I remember it was back to my high school years, fooling around with chemicals in my upstairs lab at the old farm house on the Litchfield Road in Farmingdale Maine. I was trying to make make hydrogen. All you do is add zinc to sulphuric acid. What could possibly go wrong? The sulphuric acid turns into zinc sulphate and hydrogen when you add zinc. You must capture the bubbles in a glass jar with a rubber stopper in the top and glass tubing leading off to the side. I needed to prove that the bubbles being released were really hydrogen so I lit a match. At the time, all of this seemed perfectly reasonable to my teenage brain. The part that perhaps isn’t quite so reasonable is that my brain still works the same way!

Ever want to galvanize something? Oh come on, you must have wanted to at some point. Electroplating is so cool. You have these two electrodes (I know) and you have this electrolyte (it just keeps getting better) and then you have a power supply. The electricity actually passes through the electrolyte and plates some of the metal from one electrode onto the other. If one electrode is a piece of zinc and the electrolyte is zinc sulphate then the other electrode can be any piece of metal that you want galvanized.

Zinc sulphate is harmless and is used as fertilizer. I purchased 1kg from a plant supply business for $NZ14.00. I mixed 300 grams of zinc sulphate into 1 liter of warm water to make my electrolyte. I got my zinc electrode from a standard (not alkyline) D cell battery. Cut the battery apart and you get about 12 grams of zinc. Put the negative wire onto the piece you want to galvanize and the positive wire onto the zinc plate made form the D cell. Set the power supply to 5V and wait a few hours. The zinc plate will be completely eaten away and deposited on the negative item being galvanized.

Every year, Borderline (the ESPcat) must be hauled out of the water to have its bottom cleaned and repainted with new anti-fouling paint. Getting Borderline onto the haul-out cradle, is always a bit dodgy. Borderline is too wide for the cradle so she must be shifted around until she is centered. The last time I did this maneuver, it nearly ended in disaster so I decided to add some guide wheels to automatically center her. For the princely sum of $NZ 5.80 each, I purchased 4 of these wheels to do the centering thing.

Move It 100mm 70kg Black Rubber Fixed Plate Castor

The price is pretty cheap partly because they are not galvanized. The store didn’t have any galvanized wheels and if they had, they would have cost lots more. With only the ultra thin nickel plating that comes standard on this sort of thing, they will instantly rust when coming in contact with salt water.

I transfered about 10g of zinc to the wheel assembly. I roughly calculated the surface area of the metal parts of the wheel to be about 60,000 sq mm. Zinc has a density of 7.13 grams per 100 cu mm. 10 grams of zinc would be1.4 mm over an area of 100 sq mm. 60,000 divided by 100 equal 600. 1.4mm divided by 600 equals .0023 mm thick or 2.3 microns thick.

See the lovely wheel assembly that I turned into something truly ugly with bits of zinc sticking out all over? My very first galvanizing job. I love it! I can’t wait to finish the other three.

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