Corrosion caused by fertigation with urea and potassium chloride solutions resembles that generated by irrigation

Abstract

Corrosion is a common problem in irrigation systems consisting of metal parts. Fertigation can aggravate this phenomenon because fertilizers, once dissolved in water, usually tend to be corrosive. In this study, the effects of corrosion resulting from fertigation with solutions of white potassium chloride (10 g L−1) and urea (10 g L−1) on galvanized steel and AISI 304 stainless steel specimens, materials similar to the centre pivots and injection pumps, were evaluated by simulation tests. During the experiment, the mass loss, corrosion penetration rate, thickness loss and estimated useful life of the specimens were calculated. The results showed that the variation in the fertilizer source as well as the type of metal influenced the corrosion effects. Furthermore, the useful life expectancy of steels intended for irrigation in systems that practice fertigation practically does not differ from the systems where only irrigation is practiced. The corrosion resistance of stainless steel is significantly higher than that of galvanized steel, so its use should be considered in irrigation systems. In addition, it is interesting that the Zn coating on the galvanized steel pipes used for irrigation presents at least twice the thickness to ensure greater protection of the steel substrate.