The effect of acidity and salinity level in erosion-corrosion performance of metals

  • Georgios Karafyllias

Student thesis: Doctoral Thesis

Abstract

The current study comprises an extended investigation of the effect of acidity and salinity levels on the erosion-corrosion behaviour of metallic materials used in the mining industry. In such environments, the level of both acidity and salinity significantly affects the alloys used for manufacturing either critical parts of pumps or pipelines that are subject to erosion-corrosion. The experimental approach consists of a detailed analysis with regards to the tested materials microstructure and their erosion-corrosion performance. In addition, the synergistic effects between erosion, sliding abrasion and corrosion were investigated by implementing electrochemical techniques. The post-test analysis enabled the evaluation of the materials behaviour in different hydrodynamic regions. The scope of the tested materials focused on white cast irons with either austenitic or martensitic matrix and various carbide volume fractions, whilst their erosion-corrosion performance was compared with commercial grades of stainless steel with austenitic and martensitic structure. The findings demonstrate that in neutral pH conditions and seawater the martensitic matrix and eutectic carbides are the optimum combination for the white cast irons, which are superior over the stainless steels. The increase of carbide volume fraction in conjunction with the presence of coarse/large carbides impair the erosion-corrosion performance of white cast irons. In acidic testing environment, the austenitic alloys exhibit substantially lower volume loss than the martensitic materials and this is associated with the enhanced corrosion resistance of austenitic structure. The current study extends to erosion-corrosion analysis in both neutral and very strong acidic conditions, in which two innovative alloys precipitated by σ-phase were investigated. The results illustrate that the controlled formation of σ-phase is beneficial in terms of erosion-corrosion.Furthermore, by increasing the salinity, the corrosion rates and the overall volume loss are higher on martensitic alloys with moderate corrosion resistance, whilst on austenitic or martensitic alloys with relatively good corrosion resistance the salinity has no effect.
Date of Award1 Jan 2017
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde & Weir Group plc (The)
SupervisorAlexander Galloway (Supervisor) & (Supervisor)

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