Corrosion of mild steel and protection against it in environments of a liquid mineral fertilizer – ammonium sulphate

• G.E. Gornostaeva, G.V. Redkina and Yu.I. Kuznetsov

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

Abstract: In the present article the corrosion-electrochemical behavior of St3 mild steel in liquid mineral fertilizer (LMF), namely in ammonium sulfate, at different concentrations (5, 10, 25, 40%) and temperatures (20 and 50°С) as well as its contact duration with metal was studied. Assessment of corrosiveness of LMF included the study of steel corrosion in three areas: in the liquid volume, in saturated vapor above the solution and along the waterline. The results of electrochemical and corrosion tests showed that the maximum corrosion rate of steel at 20°C was observed in a 10% (NH₄)₂SО₄ solution, and the minimum was in a 40% solution. All investigated (NH₄)₂SО₄ solutions at 20°C are characterized by a decrease in the corrosion rate of steel over time. Increasing the temperature of LMF to 50°С leads to an acceleration of corrosion of mild steel, especially along the waterline and in the vapor-gas phase. At the same time, the dependence of corrosiveness of LMF on its concentration does not change. In general, the highest corrosion rate of St3 steel is observed when it is partially immersed in (NH₄)₂SО₄ solution regardless of its concentration and temperature due to the intensification of metal dissolution in the waterline region. The maximum corrosion rate of steel was 0.7 mm/year in 10% (NH₄)₂SО₄ solution at its partial immersion and 50°С. The protective effect of mixed corrosion inhibitor based on amino alcohols and organic acids (GSMCh) in relation to mild steel in the most corrosive 10% (NH₄)₂SО₄ solution both in the liquid bulk and in the vapor phase was shown.

Keywords: mild steel, corrosion, liquid mineral fertilizers, ammonium sulfate, corrosion inhibitors

Int. J. Corros. Scale Inhib., 2022, 11, no. 4, 1802-1818
doi: 10.17675/2305-6894-2022-11-4-25

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