Industries, including medical components, that have used stainless steel or chrome plated alloy steel are turning to the use of anodized aluminum. This has increased the demand on anodized aluminum to meet the challenge to withstand aggressive environments such as alkaline attack at pH values up to 13 and acid attack at low pH values. Until now, the efficacy of the seal layer as a corrosion barrier for anodic aluminum oxide (AAO) has depended upon its depth of penetration and end composition. Structural change by way of the structural dissolution and precipitation during conventional sealing has increased corrosion resistance, but the barrier to corrosion protection has been limited to working environments that do not challenge the high pH range, with the most robust sealed AAO finishes achieving a working pH of at most, 9. Working within the realms of standard technology, a new patent-pending process has been developed that increases the efficacy of the seal by actually producing, within the sealed AAO structure, a change of state from amorphous to crystalline. The structural change produced by this seal, together with an AAO structure produced via parameters that yields a robust structure when compared to AAO produced by way of conventional parameters, immediately raised the ability of the AAO finish to withstand high alkaline and high acid environments by providing a crystalline barrier at the base of the seal reaction layer.

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