Regression Model of Factors Influencing the Corrosion Rate of X80 Steel in Silt Based on an Orthogonal Test

This paper reports a study on the influence of soil environmental factors on the corrosion of underground pipeline steel. By designing a three-factor and three-level orthogonal experiment, the correlations between three typical soil environmental factors, temperature, Cl- salt content and SO42- salt content, and the corrosion rate of pipeline steel were analysed. According to the range analysis, the main controlling factor is temperature, and the optimal solution, that is, the highest corrosion rate of pipeline steel, is when the Cl- salt content is 2.0%, the SO42- salt content is 0.3%, and the temperature is 10 degrees C. Considering the influence of the above three factors on the corrosion rate of steel samples, five regression models were established to analyze the sensitivity and influence degree of the three factors on the corrosion rate. Compared with the multiple primary regression model, the multiple quadratic regression model obtained an average relative error of only 2.62%, indicating certain feasibility of the model. The corrosion rate of steel samples was positively correlated with the temperature and the salt content of Cl-, that is, the higher the ambient temperature, the higher the salt content of Cl-, and the faster the corrosion. It also showed a first upward-then downward trend with the salt content of SO42-, that is, when the salt content of SO42- increased to a certain value, the occurrence of corrosion would be inhibited. The residual analysis indicated that the influence of the salt content of SO42- on the corrosion rate was not significant. Establishment of a corrosion prediction model has certain theoretical significance and application value to improve the reliability of underground pipelines, prolong the service life of pipelines, reduce production costs, and ensure life safety and economic benefits.