Benefits of Solids Removal from Chromate Deoxidizer Process Bath

The intention of this paper is to evaluate the benefits of solids removal via filtration from a chromate deoxidizer process bath used in desmutting aluminum alloys prior to chromic acid anodizing. It will illustrate the operation of the filtration process and its effectiveness in solids removal in this application. It will also analyze the costs associated with the process with and without filtration, including the impact on subsequent processing of parts and waste disposal.

The basis of this paper is an actual filter installation at the Fabrication Division of Boeing Commercial Airplane Company in Auburn, WA, from which all past and current data were collected. The problem being addressed is objectionable stains on aluminum parts, which occur after 5 to 6 months of bath operation. Such stains were attributed to sludge buildup in the deoxidizer. The contention is that sludge removal extends bath useful life and significantly reduces overall process costs.

The conclusion will demonstrate that filtration of the chromate deoxidizer is beneficial in extending bath life and also benefits subsequent processing.