INFLUENCE OF SURFACE ROUGHNESS ON THE PITTING CORROSION BEHAVIORS OF STAINLESS STEELS IN DIFFERENT ENVIRONMENTS by Kim Hong CHEONG Thesis Supervisor: Kin Ho LO M.Sc. in Electromechanical Engineering In this thesis, the surface roughness effect on pitting corrosion resistances of different types of stainless steels in pure water, 3.5wt% NaCl and 10wt% HNO3 have been investigated. The five stainless steels (SSs) studied in this thesis are the AISI 201 and AISI 316 austentic SS, the AISI 410 martensitic SS, the AISI 430 ferritic SS and the 7MoPlus duplex SS. These SSs were given different surface roughnesses by grinding with 80#, 400#, 800# abrasive papers and polishing as mirror-like surface with 0.7-0.1 µm of diamond paste. In 3.5wt% NaCl, reducing surface roughness has a beneficial effect for all the five stainless steels. In pure water, surface roughness does not appear to be a significant factor affecting corrosion performance. In 10wt% HNO3, the effect of surface roughness is not significant for all the five stainless steels.