Method and apparatus for controlling the degree of hydration in sealing of anodized aluminum

DETAILED DESCRIPTION I claim: 1.
In the process for producing a sealed, anodized film on an aluminum surface, said process including the steps of anodizing said surface so as to produce a porous aluminum oxide film on said surface and thereafter sealing said surface, in which the improvement comprises a process for evaluating the degree of hydration during said sealing step including the step of measuring the mixed potential of the anodized aluminum surface; electrically recording said mixed potential with respect to time; and then automatically terminating said sealing step when said mixed potential equals a predetermined voltage representative of the preselected degree of hydration.
2.
The process for evaluating the degree of hydration during sealing of an anodized aluminum part immersed in a sealing solution, comprising the steps of: measuring and recording the mixed potential of said anodized aluminum part during said sealing, and continuing said measuring and recording of said mixed potential when said mixed potential does not exceed, in a predetermined time internal, a predetermined voltage level representative of desired hydration level in order to evaluate the quality of said sealing solution.




Description:
It has long been known that anodized aluminum surfaces must be sealed to inhibit corrosion of the aluminum when in use.
The means for sealing the porous surface created by anodizing is to immerse the newly anodized part in hot water for a span of time.
The water combines with the generated porous oxide and seals it off to prevent corrosion of the aluminum.
One means of determining when the part has been sufficiently sealed is to determine the weight percent of hydration by gravimetric control.
Painted aluminum parts must be sealed sufficiently to prevent corrosion and also provide a surface to which the paint will uniformly adhere.
It is known that undersealing will provide an excellent surface for paint, but will allow corrosion of the aluminum; and that sufficient or oversealing will prevent corrosion, but oversealing may cause crazing of a painted surface