A Study On The Corrosion Behavior Of Welded 304 Stainless Steel

Goo , Chay Shuen (2011) A Study On The Corrosion Behavior Of Welded 304 Stainless Steel. Project Report. UTeM, Melaka, Malaysia. (Submitted)

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Abstract

Austenitic stainless steels find important and variety application such as construction materials in chemical and petrochemical industries, civil engineering, marine, shipbuilding, oil and gas exploitation, and et cetera. 304 stainless steel is one of most popular austenitic stainless steel used for bottom hull of ship structure. Nevertheless, welding of stainless steels alter the stability of the passive layer causes the corrosion issue arises when it is exposed to the marine environment. This work is aim to determine the effect of pH and temperature on the corrosion behavior of welded 304 stainless steel. An immersion test and electrochemical test (Tafel Slope) were employed in order to obtain the corrosion rate of the steel. Two types of samples were used in this project; unwelded and welded 304 stainless steels. Temperature and pH of the 3.5% NaCl solution are the parameters that involve in determining the corrosivity of the welded 304 stainless steels. Electrochemical test results showed that pitting corrosion in welded samples were more severe in acidic solution (pH3) at higher temperature (95±5°C) than alkaline solution (pH 12) at room temperature (25±5°C). Moreover, in immersion test the result indicated that the highest weight loss rate and corrosion rate was in pH 3 at 95±5°C for both 7 days (0.1460 mm/yr) and 14 days (0.2812 mm/yr). For instant, the welded samples given the highest corrosion rate compared to unwelded samples for both immersion test and electrochemical test. Furthermore, mechanical test for tensile test and hardness test of weldments decrease when subjected to high temperature (95±5°C) and acidic solution (pH 3). Visual inspection and optical microstructure (OM) were used to examine the microstructure features of the test samples before and after corrosion attacked as well as recognized types of corrosion form on the samples.

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