Abstract
The thermo–mechanical treatments and cyclic annealing processes have the potential of optimizing the corrosion performance of carbon steels in corrosive environments. Herein, an attempt has been made to optimize the corrosion performance of AISI 1345 steel in hydrochloric acid by thermo–mechanical cyclic annealing treatments. AISI 1345 steel was produced and cast in the laboratory and subjected to three types of thermo–mechanical cyclic annealing treatments (TMCA). The first TMCA treatment comprised hot rolling at 1050 °C followed by oil quenching and single austenitizing at 900 °C followed by furnace cooling (TMSA). The second and the third TMCA treatments involved similar hot rolling processes with double austenitizing and furnace cooling (TMDA) and triple austenitizing and furnace cooling (TMTA) processes. Microstructure analysis showed that dual-phase (retained austenite + pearlite) microstructure was achieved after all TMCA treatments with an exception of secondary phase particles precipitation after TMSA treatment. Maximum fractions of retained austenite and minimum fractions of pearlite were achieved after TMTA treatment. Highly refined microstructure of size 26.7 µm was achieved after TMDA treatment whereas; TMSA treatment offered coarse grained microstructure of size 254 µm. Electrochemical analysis was performed in 5 vol% HCl solution using Tafel scan technique. Results revealed that both TMDA and TMTA treatments caused three-fold reduction in corrosion rates (3.025, 2.771 mpy) compared to non-treated steel sample. After 168 h of immersion corrosion analysis in 5 vol% HCl solution, the surface of TMTA treated sample was observed to be partially covered with a very thin, crack-free oxide layer exhibiting minimum oxygen (8.16%) percentage. These features indicated that the TMTA treated sample underwent a very low-intensity minor corrosion attack of HCl solution and exhibited the best immersion corrosion performance among all samples. Electrochemical and immersion corrosion analysis results were in good agreement.
Highlights
Due to excellent mechanical properties, exceptionally low cost, and availability [1], carbon steels are widely used in industrial applications i.e., construction, automobile, power production [2], oil and gas refineries [3], chemical, petroleum, mining [4], and allied industries
The experimental AISI 1345 steel was produced in the laboratory using mild steel scrap, ferro-silicon, ferro-manganese, and carburizer in the pure as-received forms
Microstructural features of thermo-mechanical cyclic annealing (TMCA) treated steel samples were found very sensitive to the applied treatments
Summary
Due to excellent mechanical properties, exceptionally low cost, and availability [1], carbon steels are widely used in industrial applications i.e., construction, automobile, power production [2], oil and gas refineries [3], chemical, petroleum, mining [4], and allied industries. HCl, H2 SO4 , and HNO3 are commonly employed in the cleaning process of steel boilers, pickling of industrial steel circulating cooling system, ores processing, ion exchangers recovery, oil wells acidizing, and acid descaling [6,7]. In all these applications, carbon steels remain in contact with acids for a long time. The carbon steels are highly susceptible to natural corrosion in acidic environments and cause considerable economic losses, hazard problems at the workplace, and waste of manpower and materials [8]. Several strategies i.e., inhibitors [1,2,3,4,5,6,7,8,10], materials selection, cathodic protection, coatings [2], and heat-treatment [11], have been reported to control these undesirable mechanisms of degradation
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