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THE EFFECT OF H2SO4 SURFACE PRE-TREATMENT ON THE STRESS CORROSION CRACKING OF MAGNESIUM ALLOY AZ31B

The stress corrosion cracking (SCC) behaviour of Mg alloy AZ31B was investigated with respect to surface condition. Salt fog U-bend testing was used to identify changes in SCC as a result of surface conditioning pre-treatments. Six surface conditions were investigated: as-received, mechanically-polished, sulphuric acid (H2SO4)-cleaned, mechanically-polished then H2SO4-cleaned, aged H2SO4-cleaned, and acetic acid (C2H4O2)-cleaned. Results showed that the rate of SCC was accelerated and the SCC mode was intergranular for all surface conditioning treatments involving H2SO4-cleaning.
It was found that the accelerated intergranular SCC was a result of three contributing factors: a low pH, the presence of aggressive ions, and a porous film which allowed direct contact between the metal surface and the electrolyte. Characterization of the surfaces using potentiodynamic polarization and cross-sectional images of sample surfaces showed that in the absence of one of these three contributing factors intergranular SCC would not occur. / Thesis / Master of Applied Science (MASc)

Identiferoai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/18389
Date11 1900
CreatorsWilson, Brycklin
ContributorsKish, Joseph, McDermid, Joseph, Materials Science and Engineering
Source SetsMcMaster University
LanguageEnglish
Detected LanguageEnglish
TypeThesis

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