Effectiveness of a Silane Coating Against Microbiologically Influenced Corrosion of an Alumina-Particle-Reinforced Aluminum 6061-Matrix Composite Available to Purchase

The effectiveness of a self-assembled silane monolayer as protection for an alumina (aluminum oxide [Al₂O₃])-particle-reinforced aluminum-matrix composite against microbiologically influenced corrosion (MIC) was investigated. Tensile tests on coated and uncoated composite samples were conducted after microbiological exposures, and the effectiveness of these coatings against MIC was reported through mechanical strength and strain-to-failure measurements. Application of the silane monolayer to the composite surfaces was found to prevent degradation of the ultimate tensile strength (UTS) and strain-to-failure of the composite material in the fully annealed (temper designation: O) condition. In contrast, the UTS and strain-to-failure of the as-received extruded material (temper designation: F) were relatively insensitive to the corrosive effects of the marine Pseudomonas bacteria. Potentiodynamic corrosion measurements showed that the uncoated samples had a slightly lower pitting potential than the coated samples. Corrosion rates extrapolated from the electrochemical measurements (Tafel plots) were highest for the uncoated samples in the presence of the bacteria. Corrosion pitting on the surface of the annealed aluminum composite samples was localized, while no significant localized corrosion pitting was observed on the surface of the as-extruded material. These observations were used to explain the results of the mechanical tests and electrochemical measurements. This study demonstrates the deleterious effects of microbiologically influenced corrosion on the mechanical properties of aluminum-matrix composites; the effect of mechanical processing on the propensity of microbiologically influenced corrosion; and the potential for developing fast, easy, and cost-effective MIC protection for metal-matrix composites using silane self-assemblies.