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Correlation between accelerated laboratory tests and field tests for filiform corrosion of painted aluminum alloy sheets for automobile was investigated by conducting six kinds of laboratory tests with different pH, dry-wet condition, etc., and two sites of outdoor exposure tests, and vehicle test. It was found that susceptibility to filiform corrosion in the laboratory tests increased with the decrease of pH and/or the increase of repetition rate of wet/dry cycle. The susceptibility in the laboratory tests also increased with the increase of Cu contents in the alloy or with the sanding treatment before painting. The same tendency was obtained in the outdoor exposure tests and vehicle test. However, the correlation of the outdoor exposure tests and the vehicle test was low. In conclusion, the laboratory tests with relatively low wet ratio (70%) correlated well with the outdoor exposure tests, and the tests with relatively high wet ratio (95%) correlated well the vehicle tests.

This paper discusses a portion of a larger program on filiform corrosion concentrating on test methodologies and environmental mechanisms that contribute to filiform corrosion. It is organized into four sections, the first covers background of filiform corrosion, materials used in the study, and procedures for the sample preparation and testing. Following this, there are sections on outdoor testing, accelerated testing, and environmental parameters all of which include some procedural information, results and conclusions.

Increasing use of aluminum in automotive components has led to lower fuel consumption and enhanced performance of automotive designs. From a manufacturing standpoint, aluminum provides the additional advantage of utilizing same processes as steel. Performance and durability of painted aluminum cars, however, is dependent on proper optimization of process conditions. As part of an extensive study of factors influencing corrosion resistance of painted aluminum, the present study deals with the influence of pretreatment and coating variables and the interaction of alloy composition with zinc phosphate and electrocoat. Interfacial analysis of corrosion products indicates the relative influence of alloying elements on stability of the metal/phosphate/electrocoat interface. As a result, guidelines and recommendations on aluminum processing in an automotive manufacturing floor have been developed.