A Comparison of Thermally Sprayed Aluminum (TSA) Degradation Behavior under Immersion and CUI Simulation Conditions

Abstract Thermally Sprayed Aluminum (TSA) is used as a protective coating to protect against internal and external corrosion in different industrial applications. There has been not much work to understand the tribological and corrosion behavior of TSA from corrosion under insulation (CUI) at elevated temperatures. Most of the reported studies on TSA have either been focused either on immersion tests or ambient temperature CUI tests. This research work unveils comparative behavior of TSA at elevated temperatures when tested in CUI simulation cell (per ASTM G189-07) versus that in the immersion condition in an autoclave environment using thermal insulation's leachate extract. The corrosion tests were conducted using isothermal wet (IW) and cyclic wet (CW) conditions per ASTM G189-07 deploying linear polarization resistance (LPR) scanning, followed by detailed microstructural characterizations using confocal laser microscopy, surface topography, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). TSA coating subjected to CUI environment manifested significant wear from the flashing moisture and active substrate corrosion unlike immersion conditions where there was merely dissolution of iron particles embedded in the TSA matrix.