Multiple Regression Corrosion Models and Corrosion Mechanism of High Chromium Cast Iron under Phosphoric Acid Medium Condition

Abstract

The corrosion property of high chromium cast iron was test under different phosphoric acid medium concentration. On the base of experimental data, the binary equation model of corrosion weight loss (W) versus phosphoric acid concentration and corrosion time (c, t) was built using multiple regression analysis, which can predict corrosion property of high chromium cast iron effectively. The prediction results show that the corrosion weight loss rises lineally with increasing corrosion time, and the corrosion rate rises quadratically with increasing phosphoric acid concentration. The corrosion failure mechanism is that chromium composite carbides (M7C3) stand out of matrixes surface after the matrixes composed of martensite and austenite are corroded firstly, then the M7C3 carbides drop out of matrixes when the matrixes can not wrap M7C3 carbides, resulting gradual corrosion of high chromium cast iron. The prediction values have sufficiently mined the basic domain knowledge of corrosion process of high chromium cast iron under phosphoric acid medium. Therefore, a new way of predicting corrosion property according to corrosion conditions was provided by the authors.