Have you ever been annoyed by the white corrosion-like stuff on your anodized parts, which can be wiped off quite easily but underneath the corrosion, there are tiny pits that are barely visible? It is most likely galvanic corrosion has occurred in your process.

Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially when it is in contact with a different type of metal and both metals are in an electrolyte.

Galvanic corrosion is fairly common in organic dye baths. Assuming you use titanium racks, these racks have lower electrical potential than aluminum parts. The dye solution in this instance is the electrolyte, which allows a very small galvanic current to flow between the processed aluminum parts and the titanium racks used to hold parts. Therefore, make sure that the load bar or racks are insulated from the tank by a plastic or rubber insulator when the dye tank is metal.

In some cases it is possible to transfer the corrosion by magnesium as a sacrificing anode. It can be done by putting a magnesium bar or rod directly on the load bars with the parts or attach it to the rack. If the above effort fails, it probably means that there is too much titanium ion the tank in relation to the amount of aluminum on the load and a smaller titanium rack should be used.

On the other hand, if the dye tank is more than a year old, it is very likely that it is contaminated. Make sure to use only high quality DI water when you start a new tank. It helps to have a DI rinse before the dye tanks to lessen the possibility of dragin from a less than clean rinse.

Sometimes white powdery "bloom" can occur on the surface of parts anodized in sulfuric acid. It is usually caused by temperature or current density being too high or local overheating due to lack of agitation. It can be prevented by cooling the electrolyte, cutting down voltage, or correct agitation.