Corrosion features and time-dependent corrosion model of Galfan coating of high strength steel wires

Abstract The Galfan coating (Zn-5%Al-RE) is widely used in high strength steel wires, which are commonly adopted in the construction of modern civil structures. The present research aims at the macroscopic and microscopic corrosion features, and the time-dependent probabilistic corrosion models of Galfan coating. To achieve these goals, accelerated corrosion experiments are conducted. The field emission scanning electron microscope and the three-dimensional surface morphometer are employed to observe the corrosive surface morphology. It is found that the macroscopic corrosion feature and the microscopic corrosion feature of Galfan coating can be divided into four stages and three stages, respectively. The increasing of average uniform corrosion depth of Galfan coating shows a parabolic law with the extension of exposure period. The dynamic generalized extreme value distribution is more suitable than other distributions in establishing the time-dependent probabilistic corrosion model of Galfan coating, and the block maximum pitting factor can be described by Gumbel distribution. Both the location parameter and scale parameter of the proposed model decrease exponentially with the extension of exposure period. In the last, an application method of the proposed model is provided by solving the problem of exposure period conversion.