Corrosion and Electrochemical Behaviors of 20 Steel and St.3 Steel in Ammonium Sulfate and Nitrophoska

It is shown that, unlike their crystalline concentrates, the saturated solutions of mineral fertilizers (ammonium sulfate and nitrophoska) cause intense local corrosion damages to 20 steel and St.3 steel. In this case, the corrosion rate attains 0.29–0.33 mm/yr and is 2.2–2.5 times higher than in distilled water. These steels corrode most rapidly during the first day and then the corrosion rate in the nitrophoska solution decreases and becomes comparable with the corrosion rate in distilled water. The steady-state potentials of both steels are most negative in the solution of ammonium sulfate, whereas the corrosion currents are maximum in the nitrophoska solution. The difference between the Tafel constants b c of the cathodic reactions for both steels in the investigated media is insignificant and the lowest constant b a is observed in the nitrophoska solution, which corresponds to the lowest polarization of the anodic reaction.