Influence of the Extracts of Plant Raw Materials on the Corrosion-Fatigue Fracture of Steels in Fresh Water

摘要

The necessity of taking into account the contribution of corrosion-fatigue fracture is substantiated. Together with corrosion and salt deposition, this type of fracture complicates the reliable operation of heat-exchange systems. An important role of the deformation of specimens in the variations of the wettability of steel surface by water and inhibited solutions is demonstrated. It is shown that the increase in the level of strains in the specimen intensifies the hydrophilization of the steel surface. The wetting angles of the steel surface by aqueous extracts of oak are lower than the angles of wetting by water in the entire investigated strain range (1.86-13.3%), which corresponds to the predominant adsorption of the components of inhibitors as compared with water. It is shown that if water periodically wets the specimen surface, then it significantly decreases the resistance of steels to the corrosion-fatigue fracture as compared with air. The oak-bark extract (2 g/liter) increases the resistance of steel to this type of fracture for low levels of loading by a factor of 2.6 as compared with water. Moreover, the mechanism of fracture in the stage of crack origination changes from the intergranular fracture in water to the transgranular fracture in the inhibited medium. This enables to recommend the inhibitor based on the oak-bark extract not only for the retardation of corrosion processes but also for the inhibition of corrosion-fatigue fracture.