Organic corrosion inhibitors: where are we now? A review. Part III. Passivation and the role of the chemical structure of organophosphates

Abstract

This article continues the review of studies (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016) dealing with the passivation of various metals by solutions of organic corrosion inhibitors. It provides an overview of papers on the passivating properties of organophosphates, their complexes and salts. The results of corrosion and electrochemical studies, as well as studies on the composition and structural features of surface layers on metals by a variety of physicochemical methods are considered. Organic phosphorus compounds are often called organophosphates, especially in the case of pesticides and even toxic agents. Of course, it is unlikely that such materials have application prospects for the inhibition of metal corrosion. That is why in this series of reviews we consider organophosphates in a narrower sense limited to phosphoric acid esters and their salts, as well as phosphonic acids, their salts or complex compounds with metal cations [1][2][3][4]. The easy synthesis of acid esters of phosphoric acid, the stability of mono-and disubstituted ester anions, their ability to form complexes and hydrophobic passive films on oxidized metal surfaces has been known for a long time [1]. They can be used for the passivation of phosphated metal surfaces, and their salts with amines are used within deicing formulations. These salts can inhibit not only corrosion but also formation of deposits, so they are used in two-phase systems in the oil industry. Since higher homologues are more effective, the solubility of alkylphosphonic acids is commonly increased by ethoxylation. Salts of these acids are used in cooling lubricants, e.g., waterbased cutting fluids. The low toxicity, ability to be chemisorbed on a metal surface, and some useful technological properties of acid esters of phosphoric acid continue to motivate researchers to look for effective corrosion inhibitors of various metals among these compounds and to study their protection mechanisms [5][6][7][8][9][10][11][12][13][14]. Key words: metal corrosion, inhibitors, metal passivation, organophosphates.

Relationship between the inhibition and antioxidant properties of the plant and biomass wastes extracts – A Review

“…Most of the used synthetic inhibitors are toxic for living organisms and also to the surrounding environment because of their multistep synthesis and use of conversional energy source for heating. Those are associated with huge discharge of environmental malignant chemicals into the environment and reduced yield due to their association with several workups and purification process [14][15][16][17][18][19][20].…”

Apricot pomaces extract (Prunus Armeniaca L.) as a highly efficient sustainable corrosion inhibitor for mild steel in sodium chloride solution

“…Nowadays, mild steel is known as the most famous alloy in a wide range of industrial applications such as metal processing, equipment, and construction [1][2][3][4][5][6]. Corrosion inhibitors are commonly used in industry to reduce the corrosion rate of metals and alloys.…”

“…For mild steel protection in chloride-containing media, a large number of inorganic and organic corrosion inhibitors have been studied. The use of traditional corrosion inhibitors is now limited because of an increasing concept of "green chemistry" in the field of science, technology, and engineering [1][2][3][4][5][6]. This has prompted researchers to find out some cheap and effective "green" inhibitors [1,[7][8][9][10][11].…”

Protection of metals in phosphoric acid solutions by corrosion inhibitors. A review

“…General issues of inhibitor protection of metals and alloys in aqueous media, as well as the specifics of the mechanism of action of various groups of metal corrosion inhibitors (CI) in these media are addressed in the monograph [20] and reviews [21][22][23][24][25][26][27]. However, these studies provide no detailed examination of the specifics of using CI for the protection of metals in acid solutions.…”