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. A study conducted by the Department of Mechanical Engineering at Virginia Tech used 3 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 The corrosion fatigue data, expressed in thousands of cycles to failure, were recorded as follows:

1. Perform an analysis of variance with α = 0.05 to test for significant main and interaction effects.

2. Use Duncan’s multiple-range test at the 0.05 level of significance to determine which humidity levels result in different corrosion fatigue damage.