Data evaluation of the corrosion resistance properties of selected stainless and alloy steels in dilute electrolytes

Abstract

Comparison of the corrosion resistance of 304 austenitic stainless steel (304ST), Atlas F20S ferritic stainless steel (F20ST) and X77CrZn5 alloy steel (X77ST) was studied in 2 M H2SO4 solution at specific NaCl concentration. Corrosion resistance of 304ST varies with changes in NaCl concentration whereas the values observed for F20ST and X77ST were non-proportional. The alloys exhibit relative stability with respect to exposure time after few hours. Lower NaCl concentration results in higher corrosion rate for 304ST. The final corrosion rate values ranged from -0.029 mm/y at 0% NaCl to 0.261 mm/y at 3.25% NaCl. The values for F20ST andX77ST varied from -0.068 mm/y to 0.394 mm/y, and 2.406 mm/y to 0.348 mm/y. Without NaCl, 304ST exhibited the highest corrosion resistance at -0.029 mm/y compared to X77ST which exhibited the highest corrosion rate value of 2.406 mm/y. With NaCl 304ST has the highest average corrosion rate and X77ST has the lowest. Data from ANOVA analysis showed NaCl concentration is the dominant factor influencing the corrosion behaviour of the alloys at 99.74%, 99.08% and 97.05% compared to exposure time. The average corrosion rate values for 304ST varies slightly with respect to NaCl concentration compared to the values obtained for F20ST and X77ST signifying thermodynamic stability. The percentage of corrosion rate values for 304ST, F20ST and X77ST below 1 mm/y without and in the presence of NaCl concentration are 100%, 100% and 0%, and 76%,76% and 100%.