N-HETEROCYCLE ORGANIC-COMPOUNDS AS ADDITIVES IN THE A-C COLORING OF ANODIZED ALUMINUM FROM NICKEL SULFATE-SOLUTIONS .1. EFFECT ON COLOR INTENSITY AND UNIFORMITY OF THE PROBES

The 2-, 3-, and 4-piperidinecarboxylic acids, the 2-, 3-, and 4- pyrid inecarboxylic acids, as well as L-proline, L-hydroxyproline and L-azet idine-2-carboxylic acid were used as additives in the electrolytic col oring of anodized aluminum from nickel(II) sulfate-boric acid solution s. Their influence on the color uniformity (TP) and color intensity of the probes was investigated and correlated with their structure. This influence seems to depend on their aromatic or saturated character, t he position of the carboxyl group in the molecule and, finally, on the number of carbon atoms in their rings.