Anticorrosive behavior of steel coated with epoxy. Organic coatings that use epoxy resins are widely used for protecting steel and metal against weathering and corrosion. Researchers at National...

Anticorrosive behavior of steel coated with epoxy. Organic coatings that use epoxy resins are widely used for protecting steel and metal against weathering and corrosion. Researchers at National Technical University (Athens, Greece) examined the steel anticorrosive behavior of different epoxy coatings formulated with zinc pigments in an attempt to find the epoxy coating with the best corrosion inhibition (Pigment and Resin Technology, Vol. 32, 2003). The experimental units were flat, rectangular panels cut from steel sheets. Each panel was coated with one of four different coating systems, S1, S2, S3, and S4. Three panels were prepared for each coating system. (These panels are labeled S1-A, S1-B, S1-C, S2-A, S2-B, ..., S4-C.) Each coated panel was immersed in de-ionized and de-aerated water and then tested for corrosion. Since exposure time is likely to have a strong influence on anticorrosive behavior, the researchers attempted to remove this extraneous source of variation through the experimental design. Exposure times were fixed at 24 hours, 60 days, and 120 days. For each of the coating systems, one panel was exposed to water for 24 hours, one exposed to water for 60 days, and one exposed to water for 120 days in random order. Following exposure, the corrosion rate (nanoamperes per square centimeter) was determined for each panel. The lower the corrosion rate, the greater the anticorrosion performance of the coating system. The data are shown in the accompanying table. Are there differences among the epoxy treatment means?