Abstract
An experimental analysis was carried out to investigate the corrosivity of sensitized welded and unwelded austenitic stainless steel AISI 316, in oxidizing (H<sub>2</sub>SO</sub>4</sub>) and non-oxidizing (HCL) media. The selected samples were cut into several equal pieces. To induce sensitization, the samples were heated and soaked at 750°C at different soaking time intervals such as 30 minutes, 60 minutes, 180minutes, 300 minutes and 600 minutes followed by water quenching. The sensitized welded and unwelded samples each were subjected to immersion duration test in the oxidizing and non-oxidizing media for 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 minutes, respectively. It was concluded from the results obtained that corrosion rate of welded and unwelded decreases as soaking time and immersion duration increases at constant soaking temperature, in non-oxidizing medium of hydroChloric acid (HCL); but the decrease in corrosion rate is more in the unwelded samples. In the oxidizing medium of sulphoric acid (H<sub>2</sub>SO</sub>4</sub>); corrosion rate of the samples decreased as immersion duration/soaking time increases. However, the welded samples experienced erratic behaviour in the oxidizing medium, having a lower corrosion rate than their unwelded counterpart surprisingly, at immersion duration between 25-50 minutes as soaking time increases at constant soaking temperature of 750°C.
Highlights
Corrosion of materials [2] is the most common and most important failure mechanism in industry
One of the main reasons why stainless steels are used is corrosion resistance; they do suffer from certain types of corrosion in some environments; for instance, austenitic stainless steel is sensitive to chloride-induced stress-corrosion cracking (SCC) [19, 20]
D) The unequilibrium heat cycles, which resulted in complex reactions/phase transformation of the steel (AISI 316), during welding activities sensitized the weldment differently which significantly resulted in different corrosive impacts
Summary
Corrosion of materials [2] is the most common and most important failure mechanism in industry. Stainless steels retain its special qualities in structures because of their strength, stiffness, toughness and tolerance at high temperatures [3] Their usage in Catalytic Reformer Unit, Reactor Scallops, Vacuum Distillation Unit, Heat Tubes at Port Harcourt Refinery; process and utility areas of Mobil producing Nigeria unlimited and Chevron Escravos gas to liquid plants all in Nigeria, is a demonstration of their importance [1]. Weld decay has been observed to be common in sensitized stainless steel structures [24] These unavoidable circumstances results in heterogeneous microstructure with small amount of delta ferrite and significant segregation of major as well as minor alloying elements at the phase interfaces. This understanding would assist in mitigating the menace of corrosion in a susceptible environment as low as reasonably practicable
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
