Surface Preparation of Aluminum Alloys Using the Phosphoric Acid Containment System for Repair.

摘要

The Phosphoric Acid Containment System (PACS) was developed by The Boeing Company and is intended to provide on-aircraft phosphoric acid anodization of aluminum surfaces. The first objective of this investigation was to determine if the PACS produces a surface equivalent to the phosphoric acid tank system. The second objective was to evaluate the PACS procedure against Air Force maintenance criteria and ascertain if operator sensitivity is an issue. In addition, the PACS unit was used to study the effects of various operating parameters on the quality of the prepared aluminum surface. The operating, or processing, variables examined included voltages/currents other than those recommended in the operating procedure, anodization time/acid flow rate over the aluminum, orientation of the surface being anodized, temperature of the surface being anodized, effect of a delay between completion of acid flow and initiation of rinse, effect of fasteners on vacuum integrity and methods to seal leaks, effect of screen type, effect of type and amount of breather material, effect of the addition of sodium bicarbonate to the rinse water, and the size of the surface being anodized. Wedge test panels were made with the PACS-prepared surfaces to determine the integrity of the bond between the surface preparation and the adhesive. In addition, the surface morphology of the aluminum surface was characterized. Wedge test results indicated that the PACS-prepared aluminum surfaces were as good as those prepared using the standard phosphoric acid anodize (PAA) procedure. In addition, the morphology of the PACS and PAA surfaces were similar in overall oxide layer structure, but differed in oxide layer thickness. Based on the wedge test results, the ranges for the PACS operating or processing parameters were determined.