Use of Hydrazine for Pitting Corrosion Inhibition of Copper Sprinkler Tubes:Reaction of Hydrazine with Corrosion By-Products

Abstract

The feasibility of using hydrazine for inhibiting pitting corrosion in copper sprinkler tubes was investigatedby examining microscopical and structural evolution of corrosion by-products with SEM, EDS, andXRD. Hydrazine removed dissolved oxygen and reduced CuO and Cu2O as well. The stable phasewas changed from CuO to Cu2O or Cu depending on hydrazine concentration. Hydrazine concentrationof 500 ppm could convert all CuO corrosion by-products to Cu2O. In a tightly sealed acryl tube filledwith aqueous solution of 500 ppm hydrazine, octahedral Cu2O particles were formed while plate-likestructures with high concentration of Cu, O, N and C were formed near a corrosion pit. The insidestructure of a corrosion pit was not altered by hydrazine aqueous solution. Uniform corrosion of copperwas almost completely stopped in aqueous solution of 500 ppm hydrazine. Corrosion potential of acopper plate was linearly dependent on log (hydrazine concentration). The concept of stopping pittingcorrosion reaction by suppressing oxygen reduction reaction could be verified by applying this methodto a reasonable number of real sprinkler systems before full-scale application.