AndyW

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Here are a series of pictures revealing the mysterious process of anodizing aluminum. When you do a search on the subject you can see some wonderful and elaborate set ups. For our purposes, this is not necessary. It might look crude and Mickey Mouse, ( and it is) but it's all you need.

We are dealing with acid so all precautions must be followed. An apron, or clothes you'd use to clean out the barn. Full, wrap around goggles. Latex gloves. A paper towel dispenser nearby or rags. A fire extinguisher. Every shop should have two. VERY important is aggressive ventilation. Opening a window or two won't do. I have a 1/4HP exhaust fan with a positionable duct. The bubbles you see on the Cathode and anode are HYDROGEN. And maybe some other nasties that can burn your lungs or explode. Y'all be warned if you want to try this. Best done outside and like Lipos, never unattended.

Battery acid is available at some automotive outlets. With sealed batteries the norm these days, this may be a problem. Battery acid is not pure, it's diluted and I THINK it's 50/50 with water. We are diluting this further with 50/50 battery acid and distilled water. Note the label on the jar. If you have access to pure, sulfuric acid, take note the ratio should be 25% pure acid and 75% water.

The clamp must be made of aluminum. Where the clamp touches will leave a spot of unanodized material. In this case, we are clamping on the inside of the piston.

Your piston must be washed and rinsed 3 or more times. If water beads on it, it isn't clean. Washing once won't do it. You need to use the "water break" test. Water won't bead, it'll lay flat or just run off.

Note that the positive lead, the ANODE goes to the piece, hence the term anodizing. The negative lead is attached to a strip of lead. Make sure that the two never touch.

And that's pretty much it.

I used to use a deep discharge marine battery, my field box battery and a crude, adjustable power supply. This is my first use of a hacked computer power supply. Something to adjust the current is in the works. But in our case, to anodize a small piston, the current was just under 100 mAh so a field box battery should do just fine. It only takes 15 minutes to get a nice, grey, anodized surface on the piston and that's all we need. If you leave it in for a few hours, like I did once, by mistake, you'll find that at one point anodizing stops and corrosion sets in.

Anodizing normal grades of aluminum like 6061 will require much higher current and a longer time in the bath, at least an hour. Pistons have a high silicon content and won't anodize like most aluminums (hence the self limiting current) but what anodizing DOES occur is sufficient for our needs.

After about 15 minutes when you get a nice, grey colour, take out your piece, put it in a strainer and rinse it off under tap water. Then use a heat gun to dry it off and get it nice and hot. Lay it on a folded, paper towel and drown it in castor oil while it's hot. This will soak the pores and as the piston cools the oil will be drawn into them.

Re-assemble your engine and see if it was beneficial. Will post the results after supper.

Colour anodizing will be discussed on a separate thread.