Abstract
Characterization and corrosion behaviours of austenitic stainless steel (AISI 316) types at various concentrations of hydrochloric acid solutions were investigated in relation to its pitting corrosion resistance. Both gravimetric-weight loss and potentiodynamic polarization were used for the investigations. The AISI 316 was characterized by X-ray fluorescent (XRF). The characterization of the coupon before and after the corrosion test in various concentrations was done using scanning electron microscopy (SEM). The temperature, acid concentration and time were varied in the range of 30-60°C at 10°C interval, 0.5-2M at 0.5M interval and 1 to 6 day at 1 day interval, respectively. The XRF revealed some important elements in the AISI 316 such as (Cr, Ni, Mn, Si, C, S, P etc) which confirmed the materials to AISI 316. The weight loss results revealed that the corrosion rate decreased with increase in exposure time from day 1 to day 6. The corrosion rate of the AISI 316 increased with increase in temperature, severe to pits formation and growths with increase in concentration of acid from 0.5 - 2M. The corrosion rate of AISI 316 increases with increase in acid concentrations. The Tafel results also revealed that both anodic and cathodic sites were shifted with the lowest corrosion resistance occurring at 0.5M of HCl. The SEM of the coupons in the presence of acid revealed pits formation, growths and pitted AISI 316 surfaces. The results obtained from the weight loss, Tafel and characterization were also in good agreement.
Highlights
The world demand for fossil fuels is still growing even though alternatives to such energy are currently being sought out globally
Austenitic stainless steels have a wide spectrum of resistance to corrosion by chemical environment due to the formation of protective passive film on its surface
The chemical composition analysis conducted on AISI 316 coupon used for this study was carried out at Spectro Ametek, Materials Analysis Division, Lagos
Summary
The world demand for fossil fuels is still growing even though alternatives to such energy are currently being sought out globally. Corrosion occurs in different forms in structures made of steels during service in various environments These forms of corrosion can be intergranular, pitting, sulphide stress cracking, and stress corrosion cracking. Austenitic stainless steels have a wide spectrum of resistance to corrosion by chemical environment due to the formation of protective passive film on its surface. This film is very thin, essentially transparent and self- healing. Pitting corrosion being classified as very dangerous threat and produces pit which looks small on surface but propagate deep inside the metals This type of corrosion is considered more harmful than uniform attack. The aim of this work is to characterrize and determine the corrosion resistance of AISI 316 in different concentrations (0.5M, 1M, 1.5M, and 2M) of hydrochloric acid and temperature between 30-60°C solutions using weight loss and potentiodynamic measurement test
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