Effects of Al Content on Corrosion Behavior of High Entropy Alloys—A Review

High entropy alloys (HEAs) are a newly developed and novel class of materials that have triggered the attention of many researchers because of their excellent corrosion resistance, unique phase structure, and mechanical properties compare to traditional alloys. HEAs use concentrated blends of five or more principal elements in a nearly equimolar ratio to form an alloy base. HEAs are mainly of a solid solution with random arrangements of multiple elements. Corrosion is the biggest problem in various industries such as the oil and gas industry, aerospace industry, power plants, and infrastructure. Corrosion affects more than three percent of GDP annually. Therefore, focus on new materials that show good corrosion-resistant is very important. In this paper, an attempt is made to review the corrosion behavior of HEAs with varying Al composition. Corrosion behavior depends on many factors such as elements of HEAs, electrolyte medium, and volume fraction of content. Increasing Al content results in the Al-rich phase; thus, the volume fraction of other elements such as Cr decreases, and corrosion resistance decreases while Al addition also changes the microstructure which affects the corrosion behavior. It has been observed that HEAs show good corrosion resistance compare to conventional alloys. Critical aspects, detailed observation, and a summary of previous work are presented which may help researchers to get useful information in subsequent research in this domain.