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

• Ya.G. Avdeev

A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119071 Russian Federation

Abstract: The article summarizes the literature data and patents on the protection of steels and nonferrous metals in phosphoric acid solutions with various corrosion inhibitors. Some aspects of practical use of H₃PO₄ solutions, their properties and corrosivity toward various metals are reviewed. It is shown that the overwhelming majority of individual organic and inorganic compounds, as well as composite inhibitors offered for the protection of metals in this medium are of low efficiency due to weak adsorption on metal surfaces. A promising method for the protection of steels in phosphoric acid media involves the use of formulations containing triazole derivatives and sulfur-containing additives. The components of these mixtures form polymolecular protective layers on the metal surface that are highly efficient in slowing down corrosion processes even at temperatures up to 100°С. An important property of these protective layers is a strong chemical bond of the inhibitor molecules with the metal surface and with each other inside the layer. Inhibited H₃PO₄ solutions resistant to the accumulation of corrosion stimulators – Fe(III) salts – may become a new and promising field of use for this acid. The bibliographic list includes 170 sources.

Keywords: corrosion inhibitors, acid corrosion, phosphoric acid, orthophosphoric acid, steels, nonferrous metals, triazoles

Int. J. Corros. Scale Inhib., 2019, 8, no. 4, 760-798 PDF (1 110 K)
doi: 10.17675/2305-6894-2019-8-4-1

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