Traditional Anodizing To Prevent Corrosion

The practice of anodizing, or the controlled oxidation, of aluminum and its alloys are more than seven decades old.

The main intention behind anodizing aluminum and its alloy parts is to guard the highly reactive surface against corrosion in aqueous environments, like moist air and sea water.

Since the anodic coating could be produced in a range of colors, the painted parts are generally used in architectural applications.

Further, as the process of aluminum anodization on CA would produce a hard ceramic covering, harder than that of the substrate from which it is formed, the anodic coatings are also used to shield aluminum parts from abrasions, especially sand abrasion.

Traditional anodizing process is electrochemical oxidation.

The part which is to be anodized is then connected to the positive terminal of a Direct Current (DC) power source and a non reactive metal, like stainless steel, is coupled to the negative terminal.

The aluminum anode, and the stainless steel cathode are then immersed in an electrolytic bath and DC voltage is applied across them.

The potential difference is of order of 20 -100 V and the current density is 1-10 A/dm2. The electrolytic bath comprises of aqueous solutions of chromic acid, orthophosphoric acid, oxalic acid, sulfuric acid, or combinations thereof.