Erosion-corrosion resistance of engineering materials in various test conditions

Erosion-corrosion is a complex phenomenon which involves the interaction between the mechanical processes of solid particle erosion and the electrochemical processes of corrosion. A whole range of issues is faced by a designer when trying to obtain relevant information on erosion-corrosion performance of a material. Amongst the constraints are the dispersed test conditions and test rigs available in the literature making comparisons and quantifying erosion-corrosion wear rates of different materials very difficult. The aim of this work is to evaluate the repeatability of erosion-corrosion experiments and to investigate the role of different parameters influencing erosion-corrosion. The materials tested in this work are stainless steel (SS316L/UNS S31603), carbon steel (AISI 1020/UNS G10200) and nickel-aluminium bronze (NAB/UNS C63200). A slurry pot erosion tester was used as the test apparatus and test parameters such as erodent size, erodent concentration, flow velocity and test solutions were varied to study their effect on erosion-corrosion. SEM analysis showed that a similar erosion-corrosion mechanism is seen for SS316L and NAB with formation of multiple extruded lips and platelets typically seen for erosion dominated material. In contrast the surface of AISI 1020 revealed the formation of craters, pits and shallow indentations which suggests that corrosion mechanism has a dominant influence on the material. Error rates in tests were found to have an average of 5.5% which are relatively low indicating good repeatability of test measurements and data from the test rig. The erosion-corrosion resistance of AISI 1020, SS316L and NAB were compared and it was found that SS316L showed the lowest erosion-corrosion mass loss rates in all test conditions followed by NAB and then AISI 1020. However in terms of synergistic ranking, NAB showed the best resistance to the combined action of erosion and corrosion with the highest negative synergy value. Positive synergy was evident for AISI 1020 in 3.5% NaCl and SS316L in 0.3 M HCl. A wear map is presented to evaluate erosion-corrosion trends of the materials. This work combines the assessment of test repeatability, variation in test conditions and comparison of material performance which are key stages in a material selection process. (C) 2009 Elsevier B.V. All rights reserved.