EFFECT OF THE HEAT TREATMENT ON CORROSION BEHAVIOR OF ELECTROLESS NICKEL COATINGS DEPOSITED ON BEARING STEEL TESTED IN AN ALKALINE ENVIRONMENT

RIP2025-00057: The food and beverage industry faces significant challenges related to equipment corrosion, particularly due to chemical exposure to high alkalinity or acid environments in cleaning agents, thermal cycling, and abrasion which accelerates material degradation, produces contamination, and compromises both equipment life and product quality. To address these issues, specialized coating technologies are emerging as vital solutions. Electroless nickel coating for example has demonstrated exceptional effectiveness in preventing corrosion in harsh conditions. Particularly this coating offers outstanding properties such as uniformity, hardness, wear resistance, and high corrosion resistance. It has been stated that the coating heat treatment significantly impacts the properties of the coatings by altering their microstructure, hardness, and overall performance. These properties are directly influenced by the amount of phosphorus, temperature, and time.

Although electroless nickel coatings have been widely used in different industries, it is unknown the corrosion coating performance of heat-treated coatings in food and beverage applications. Therefore, additional research is vital to understand its corrosion behavior, especially on cleaning solutions. Therefore, this work aimed to investigate the properties and corrosion behavior of electroless nickel coating containing various amounts of phosphorous (low, medium, and high) with and without heat treatment. Heat treatment was performed in all the samples at 170°C for four hours to evaluate the influence of heat treatment. Nanohardness, morphology, and elemental composition were investigated by Nanoindentation, scanning electron microscopy, and Energy-dispersive X-ray spectroscopy. Electrochemical testing such as open circuit potential (OCP), electrochemical impedance spectroscopy, and potentiodynamic tests were used to evaluate the corrosion behavior. Preliminary results showed better corrosion resistance, with the high phosphorous heat-treated coatings. Nano hardness increased significantly with the heat treatment due to the formation of nickel phosphide phases.