Study Of Structure, Microstructure And Corrosion Properties Of AISI 304 Toward Marine Specification

Gakim, Miron (2009) Study Of Structure, Microstructure And Corrosion Properties Of AISI 304 Toward Marine Specification. Project Report. UTeM, Melaka, Malaysia. (Submitted)

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Abstract

AISI 304 is known as austenite stainless steel which has Face Centre Cubic (FCC) structure. AlSl 304 is the conventional stainless steel that had been applied in marine construction application. It is important to study the corrosion properties of AISI 304 due to the corrosion attack. Two type of corrosion attack that commonly can be found on AlSI 304 steel, which respectively are pitting and intergranular corrosion. Pitting corrosion occurs due to the attack of the corrosive environment to the heterogeneous material composition on the surface of the AlSI 304 where at the surface region, black spot that contain high iron wiU ease attack by localize corrosion and form pitting. lntergranular corrosion is occurring when AISI 304 is exposed to the beat at temperature 500 °C to 800 °C and slow quenching process. The process of rapid quenching can cure the intergranular corrosion in AISI 304. The formation of the respective corrosion is studied by using electrochemical analysis and weight loss analysis respectively. The formation of pitting corrosion and the behaviour of AISI 304 to resist pitting corrosion is studied by applying effect on temperature test and effect of pH. In this study, at high temperature, and more acidic solution, the pitting corrosion attack is increased. Potentiodynamic Cyclic Polarization and Tafel applied in analyzing this fonnation of pitting and the behaviour of AISI 304 in resisting corrosion. According to ASTM A 262-01, practice C, susceptibility to intergranular corrosion attack on AISl 304 is investigate. In this study, intergranular corrosion is jnvestigated by exposing AISI 304 at temperature 677 °C. Based on the experiment it shows that after AISI 304 exposed to 677 °C, AJSI 304 is susceptible attacked to irrtergranular corrosion. The same result is shows when exposed AISI 304 is quenched at slow quenching process. Rapid quench bad been improving corrosion behaviour of AISI 304 in resisting intergranular corrosion. The corrosion product that had been propagates on surface of AISI 304 was analysed by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). Energy Diffraction X-ray (XRD) analysis is applied to analyze the phase of Chromium Carbide form in the structure of AISI 304. This formation had been analyzed that this phases causing susceptibility to intergranular corrosion in AlSI 304. Based on the marine specification, AISI 304 is not suitable applied in direct exposed to marine environment because this material cannot resist corrosion attack due to cWoride attack and ease to form chromium carbide in AlSI 304 structure due to the exposed heat such welding process. Based on the study, corrosion rate AISl 304 in Melaka seawater is 0.019 mm/year. Marine specification to the alloy that can resist corrosion attack, the corrosion rate of the alloy should not exceed to 0.01 mm/year.

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