Pickling Kinetics of Tertiary Oxide Scale Formed on Hot-Rolled Steel Strip

During hot rolling process a steel strip covers with oxide scales. These scales have to be removed by acid pickling process. This work focuses on the study of the scale removing rate of a hot-rolled steel strip in order to find an expression explaining the rate of reaction in hydrochloric acid. The study of scale removal is accomplished by utilizing the pickling simulator with different acid concentrations and pickling temperatures. There are two approaches that can be used to find a scale removing rate; the measurement of weight change and the iron concentration change after the pickling process. In this work, the measurement of the change of iron concentration was selected because it represents the actual amount of the scale removed after the pickling process. The experimental data were used to derive the expression for the rate constants. By using these expressions, the pickling equations can be obtained. These equations are capable of predicting the maximum removable scale thickness during the pickling process for several pickling conditions; i.e. time needed for scale removal.