Back To Black Again

BACK TO BLACK AGAIN

What would be the best method to blacken aluminum? Aluminum can be anodized, treated with a solution of white arsenic (one ounce), sulphate of iron (one ounce), and hydrochloric acid (twelve ounces), all mixed in added to twelve ounces of water, and, of course, it can be painted. Are there methods of blackening aluminum that would be better than those I have mentioned?

Charles Gerwig Peekskill, N.Y.

kill,

By and large, the very best method of blackening aluminum is to have it anodized. The anodic coating is more or less permanent, and it is no barrier that would hold the heat inside the metal. The same cannot be said of any paint. Indeed, a heavy coating of paint, whatever the color, could make the engine run at a much higher temperature than would be the case with bare metal cooling fins.

I would be very careful about chemical blackening treatments. Aluminum sometimes reacts very strongly to acids, and it would be quite easy to ruin a valuable part if you didn’t know exactly what you were doing. Moreover, you must consider the possibility that the part may be of some magnesium-aluminum alloy, and magnesium is exceedingly touchy.

In general, it seems prudent to either have the blackening done by a company that makes a business of such things, or to obtain the help of a professional chemist, or to restrict your efforts to a light coating of dull black paint.