91Ó°ÊÓ

Corrosion fatigue in metals has been defined as the simultaneous action of cyclic stress and chemical attack on a metal structure. A widely used technique for minimizing corrosion-fatigue damage in aluminum involves the application of a protective coating. In a study conducted by the Department of Mechanical Engineering at the Virginia Polytechnic Institute and State University, different levels of humidity- Low: \(20-25 \%\) relative humidity Medium: \(55-60 \%\) relative humidity High: \(86-91 \%\) relative humidity and 3 types of surface coatings Uncoated: no coating Anodized: sulfuric acid anodic oxide coating Conversion: chromate chemical conversion coating were used. The corrosion-fatigue data, expressed in thousands of cycles to failure, were recorded as follows: (a) Perform an analysis of variance with \(\mathrm{a}=0.05\) to test for significant main and interaction effects. (b) Use Duncan's multiple-range test at the 0.05 level of significance to determine which humidity levels result in different corrosion-fatigue damage.