The importance of corrosion studies brings to the forefront economic losses, damage, and safety issues of metals deterioration in the construction industry. Although the choice of a material and use of inhibitors can contribute to its resistance to environmental corrosion behavior, the structural deterioration of metals can be exacerbated under operation conditions. In this review, highlights of research findings published in the past five years on the use of plant materials as corrosion inhibitors for variants of steel: carbon steel, mild steel, stainless steel are provided. It elucidates the meaning of green inhibitors and their types. It also presents the methods employed to ascertain the inhibition efficiencies of the plants/plant parts listed and the parameters considered in the corrosion inhibition analyses. The major gaps or limitations identified in the reported research findings include experimentation at constant temperatures and short immersion periods for the alloys. Due to the fact that, if these extracts were to be deployed for industrial use, they'd be subjected to more hazardous conditions, such as higher temperatures, pressures, etc., this paper proposes that their investigations as potential inhibitors on the laboratory/pilot scale be performed at higher temperatures and longer immersion times which may as such provide more comprehensive knowledge on the environmental/climatic requirements for their application. Additional improvement strategies are also suggested. The list of extracts, however, is not exhaustive.

Research into the use of safe and environmentally friendly corrosion inhibitors can pave the way for an understanding of their inhibition mechanisms in metallic alloy materials. This review seeks to present and discuss the research work reported in the literature on the use of amino acids and their derivatives as corrosion inhibitors for iron and its alloys in different aggressive solutions. This non-toxic, biodegradable and relatively cheap corrosion inhibitor has shown to be efficient as an inhibitor for metals/alloys in acidic, alkaline and neutral solutions depending on experimental conditions. Electrochemical and surface techniques were among the most often used techniques to evaluate the corrosion inhibition efficiency of amino acids. Highest values of inhibition efficiency can be obtained in the presence of ions as Iand Br. This review presents and discusses most of the contributions made in literature on the use of amino acids and their derivatives as corrosion inhibitors for iron and its alloys.

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