Erosion-Corrosion Rates of Corrosion-Resistant Alloys Under High-Velocity Multiphase Conditions

The erosion-corrosion behavior of two corrosion-resistant alloys (UNS S42000 and UNS N08028) has been assessed under gaseous-liquid-solid impingement conditions. Erosion-corrosion impingement tests were conducted at three different impact angles and at three different impact velocities up to 60 m/s, and furthermore, pure erosion and pure corrosion impingement tests were run for UNS S42000, and carbon dioxide (CO₂) at a pressure of 1,500 kPa was used as the gas phase. The sand content, with grain size below 150 μm, was 2.7 g/L brine. Artificial brine with a sodium chloride (NaCl) content of 2.7% was used as liquid phase. The damaged surfaces of samples exposed to the high-velocity multiphase flow were investigated using scanning electron microscopy (SEM) and an optical device for 3D surface measurements to assess the depth of attack. Electrochemical investigations according to ASTM G61 were performed to determine electrochemical behavior of tested materials including critical pitting potentials (E_pit) and repassivation potentials (E_repass). Furthermore, the surfaces near regions of the samples tested were investigated using applying atomic force microscopy (AFM), magnetic force microscopy (MFM), and nano-indentation measurements. From the analysis, variation of velocity shows the greatest effect on the degradation rate of both materials. In this paper the erosion-corrosion behavior and rates of two stainless steels are presented. The effects of their chemical composition and mechanical properties are discussed.