Anodic Dissolution Behavior of Electrochemical Corrosion of High Chromium Cast Iron in a Neutral Environment

Author of the article:JIN Haini 1,2 , SUI Yudong 1,2 , JIANG Yehua 1,2 , ZHOU Mojin 1,2

Author's Workplace：1. College of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650000, China; 2. National & Local Joint Engineering Research Center of Advanced Metal Solidification Forming and Equipment Technology, Kunming University of Science and Technology, Kunming 650000, China

Key Words： high chromium cast iron; electrochemical corrosion; corrosion current density; corrosion potential

Abstract： For high chromium cast iron (HCCI) used in marine atmospheres for a long time, the different corrosion behaviors of surfaces with different crystal orientations will inevitably lead to microscopic corrosion galvanic cells and pitting initiation. By defining the corrosion behavior of different oriented surfaces and adjusting the proportion and combination of specific oriented surfaces, the galvanic corrosion sensitivity of high chromium cast iron can be effectively weakened and the corrosion rate of high chromium cast iron can be delayed. Therefore, in this paper, the corrosion potential and corrosion current density of the (100), (110) and (111) crystallographic surfaces in KmTBCr26 high chromium cast iron were calculated by first principles modelling, and the electrochemical corrosion anodic dissolution reaction polarization curves of this HCCI in a neutral NaCl environment were obtained. The results show that the surface with (100) orientation has the highest corrosion potential and the lowest corrosion current density among the three low-index surfaces, which are -0.567 4 V and -7.858 7 log(A/cm 2 ) for the ideal surfaces, respectively, showing the best corrosion resistance. However, the existence of surface vacancies and Cl adsorption can lead to an increase in the calculated results of corrosion
current density on all the three low-index surfaces, that is, the anode dissolution rate is accelerated, and the dissolution rate  gap between different surfaces is slightly reduced. At the same time, it also reduces the corrosion potential of all surfaces and slightly narrows the potential difference between different surfaces.