Aluminum alloys are not immune to corrosion which can take the form of localized corrosion. Thus, the assessment of the corrosion behavior of aluminum alloys under atmospheric conditions is a major topic for many applications including the aerospace industry. One major difficulty in this task is the lack of robust and reliable accelerated corrosion test(s) in this field. Indeed, several tests as the Neutral Salt Spray Test (ASTM B117) are used to assess the general corrosion resistance of aluminum, but these tests were not developed specifically for the aerospace industry and are not representative of service conditions. The aim of the present study was to compare the results of various accelerated corrosion tests conditions (ASTM B117, VDA 233-102, Volvo STD 423-0014) with newly developed test conditions. Hence different accelerated corrosion tests were designed by varying several parameters in the Volvo STD 423-0014 such as the salt concentration, the time of wetness and the relative humidity. The results obtained on 8 aluminum alloys were then compared to marine exposures (corrosivity class C3). From the results, one test provides the same type of corrosion attacks on the different alloys as under atmospheric exposures in the marine site and a good acceleration factor.
Aluminum alloys exhibit good resistance to atmospheric corrosion due to the presence of a fine, passive oxide layer 1,2. Nevertheless, these alloys are not immune to corrosion which can take the form of localized corrosion like pitting, intergranular or exfoliation corrosion. Thus, the assessment of the corrosion behavior of aluminum alloys under atmospheric conditions is a major topic for many applications including the aerospace industry. New alloys have been developed in the last decades including Li containing materials such as AA2050, AA2099, AA2198 3,4. Hence, there is a need to qualify these new materials. One major difficulty in this task is the lack of robust and reliable accelerated corrosion test(s) in this field. Indeed, several tests are used to assess the general corrosion resistance of aluminum, but these tests were not developed specifically for the aerospace industry. Neutral Salt Spray Test (NSST-ASTM B117) 5, for example, is widely used but it is not representative of service conditions and thus not adapted to qualify new developments. NSST-ASTM B117 should therefore only be used for quality control for systems with well-known performance in field but not for prediction of newly developed systems. Indeed, in their work, Baldwin and Smith demonstrated that some coatings characterized as poor in NSST are considered as resistant in marine atmospheric exposures6. In their work, Pathak draws the same conclusions on Mg-rich primers which failed rapidly and generated heavy blistering corrosion in NSST while they showed good behavior in marine atmospheric exposures7.
