Corrosion inhibition efficiencies of polymeric materials on alloy steel in dilute hydrochloric acid and sodium hydroxide solutions at ambient temperature

A corrosion control test was conducted on alloy steel, using polymeric coatings (polyurethane, bitumen (medium airing), and high-density polyethylene) in dilute HCl solutions of pH values 4, 7, and 12, respectively for acid, neutral and alkaline solutions at ambient temperature. In the study, Eighty-four coupons of alloy steel were used. The coupons were mechanized, ground, polished, etched with natal, and weighed using a digital weighing balance (Beva 206B). The mass of each coupon was recorded according to the tag number on them. Twenty-one of the coupons were coated with polyurethane, 21 coated with medium curing bitumen (MC), and 21 coated with high-density polyethylene, while 21 were left uncoated. Seven polyurethane-coated samples, bitumen coating, and uncoated coupons were suspended in dilute HCl solutions of pH values 4, 7, and 12. Every week, one sample is taken from each of the solutions, the coatings and the corrosion products were removed, and the coupons were etched with natal. Then the coupons were reweighed, and their masses were recorded in accordance with their tag number. The weight loss per unit area of the coupons, corrosion rate, and percentage corrosion inhibition efficiencies of the coatings was calculated over seven weeks. The results obtained were tabulated and represented graphically. From the results obtained, it is seen that the corrosion inhibition efficiency of polyurethane coatings is higher compared with bitumen and polyethylene. It is also seen from the graphs that the corrosion rate of the coupons is higher in acid, a little bit lower in alkaline, and much lower in neutral solution. It is also observed that the corrosion rates fall with time as the inhibition efficiency also falls with time

Carburization-based optimization of AISI 8620 steel using rice husks and charcoal as carburizers

This study was centered on improving the mechanical properties of AISI 8620 steel using the carburization technique. The failure in service conditions of many steel components such as cams, gears, and shafts necessitated the research as it demands that they possess both high wear-resistant surfaces and tough shock-resistant cores. Standard test samples prepared from the steel material were subjected to a pack carburization process using rice husk and charcoal as carburizers, and the energizer – calcium trioxocarbonate (IV) at temperatures of 800, 850, 900, and 950 °C, and held for 60, 90, and 120 minutes. The samples were quenched in water and tempered at 500 °C for 60 minutes. After the pack hardening process, the test samples were subjected to tensile, impact, and hardness tests. From the data obtained, ultimate tensile strength (UTS), Hardness, Young’s Modulus, engineering strain, and impact strength were calculated. The case and core hardness of the carburized samples were noted, and an optical microscope was used to observe the microstructural features of the case-hardened, quenched, and tempered samples. The responses (mechanical properties of steel) were optimized using response surface methodology to obtain the optimum carburizing conditions-temperature and holding time. Results showed that the sample’s microhardness core and microhardness case increased from 253 to 327 HV and from 243 to 339 HV as the holding time increased from 60 to 120 minutes, indicating an appreciable increase in the mechanical property of the samples. The optimum carburizing conditions were at a temperature of 885 °C and a holding time of 120 minutes. Hence, the carburization of AISI 8620 steel using rice husk and charcoal as carburizers improved the steel material’s case, core, and mechanical properties