Chromic Anodizing

              Utilizing a chromic acid electrolyte this form of anodizing yields the thinnest coatings, only .05 to .1 mils thick. Chromic anodizing is a good choice when a part is complex and difficult to rinse because chromic acid is less corrosive than sulfuric acid used in other anodizing methods. Chromic anodize also reduces the fatigue strength of the aluminum less than the other methods described.

Chromic anodize is formed by using an electrolytic solution of chromic acid that is about 100° F and a density of 1.5 to 4.5 A/ft2. The process will run for 40 to 60 minutes. This will produce a clear to gray coating, depending on sealing and alloy used, that is about 2 µm.

Advantages:

Chromic anodize offers a minimum of 336 hours 5% salt spray resistance . It is not as durable as sulphuric acid or Hard anodizing and does not accept dyes as well as sulphuric acid anodizing. Due to the low thickness, it can be an advantage of parts with tight tolerances. Also, since chromic acid is less aggressive towards aluminum than the sulfuric acid , it should be used in parts that are difficult to rinse such as welded and riveted assemblies.

Materials:

Most alloys are suitable for chromic anodizing. Exceptions would be high-silicone die-cast alloys and high-copper alloys. Basically, an alloy with more than 5% Cu, 7% Si, or 7.5% of alloying elements should not be used.

 If you want to start an anodizing unit  contact us