Effects of magnesium chloride polluted soils on underground Q235 steel pipelines

This paper discusses the effects of soils polluted with different magnesium chloride (MgCl₂) contents on the corrosion of Q235 low-carbon steel pipelines. The material has a yield strength of 235 MPa. The following major parameters were considered in the experimental study to analyze MgCl₂ polluted soils: degree of saturation S_r, electrical resistivity ρ_s, oxidation reduction potential E_h7 and corrosion potential E_corr. The corrosion properties of Q235 steel samples buried in soils, such as corrosion behavior of macrographs and scanning electronic microscopy (SEM) photos, chemical elements components of corrosive products by energy dispersive spectrometer (EDS), corrosion weight loss m_cor, corrosion rate v_cor, and dynamic equation of m_cor, were studied in detail. Based on the statistical analysis results obtained from this study, MgCl₂ has a significant impact on ρ_s, while MgCl₂ has lesser effects on other parameters. Corrosion macro and micro behaviors of Q235 steel were revealed. The v_cor of Q235 steel decreases with the increase of corrosion time (t), while it increases with MgCl₂ contents. The dynamic equation for m_cor and the pollution impact factor β for Q235 steel in MgCl₂ polluted soils are proposed. Lastly, a developed multi-linear regression equation for v_cor is recommended.