Investigating the Corrosion Behavior of Roller Plates in Two Environments of C60 Water and Fresh Water in a Pelletizing Unit

Nowadays, roller plates are used in the steel industry and pellet making unit in order to classify iron ore pellets. Roller plates or screen rolls are a type of screening device, which are used to determine size, granulation, and transfer of materials. In this research, the corrosion behavior of these rolls was evaluated in two different water environments including fresh water (drinking) and return water (C60). First, the spark spectrometry test was performed to measure the chemical composition, and then the electrochemical corrosion tests were performed on steel parts A⁺, A, B at a temperature of 25 °C. The open circuit potential test was performed to measure the open circuit potential and study the general behavior of the components. Then electrochemical impedance spectroscopy test was performed to evaluate corrosion resistance and surface conditions, potential dynamic polarization test to determine corrosion rate and, pitting test to evaluate pitting corrosion conditions. The results of these tests showed that the A⁺ part had the highest corrosion resistance and the A part had the highest corrosion rate in both environments due to the presence of a larger amount of molybdenum element in the structure of A⁺ part compared to A. Also, the results showed that the corrosion of all parts in fresh water was less than the corrosion in C60 water. The main reason for this difference was related to less aggressive ions such as chlorine in fresh water compared to C60 water. In addition to uniform corrosion and pitting corrosion, galvanic corrosion between phases in the microstructure was also determined as one of the main causes of alloy corrosion. According to the metallographic images of the parts and the hardness measurement results, the microstructure of all three parts was martensitic, which was observed in parts A, B, and delta ferrite phase in the martensitic field.