Editing Anodizing (section)

===Organic acid ===
Anodizing can produce yellowish integral colors without dyes if it is carried out in weak acids with high voltages, high current densities, and strong refrigeration.<ref name="Edwards"/> Shades of color are restricted to a range which includes pale yellow, gold, deep bronze, brown, grey, and black. Some advanced variations can produce a white coating with 80% reflectivity. The shade of color produced is sensitive to variations in the metallurgy of the underlying alloy and cannot be reproduced consistently.<ref name="sheasby ch8" />

Anodizing in some organic acids, for example [[malic acid]], can enter a 'runaway' situation, in which the current drives the acid to attack the aluminium far more aggressively than normal, resulting in huge pits and scarring. Also, if the current or voltage are driven too high, 'burning' can set in; in this case, the supplies act as if nearly shorted and large, uneven and amorphous black regions develop.

Integral color anodizing is generally done with organic acids, but the same effect has been produced in laboratories with very dilute sulfuric acid. Integral color anodizing was originally performed with [[oxalic acid]], but [[sulfonated]] [[aromatic compounds]] containing oxygen, particularly [[sulfosalicylic acid]], have been more common since the 1960s.<ref name="sheasby ch8" /> Thicknesses of up to 50 μm can be achieved. Organic acid anodizing is called Type IC by MIL-A-8625.