New environmentally friendly corrosion and scale inhibitors for industrial cooling waters

The results of the electrochemical and potentiokinetic tests concerning the efficiency of anticorrosion protection of mild steel, with selected compounds such as the alkyl-, aryl- and amine-phosphonic acids derivatives or their mixtures with Zn2+ ions and phthalic anhydride, in model water are presented. For the best inhibitive mixtures, corrosion and scale inhibition effectiveness were determined by gravimetric method after various exposure times (24 to 240 hours). Of selected inhibitor mixtures, compositions No. IV containing 50 mg/dm(3) butylenodiamino - N, N' - bis [3,4(dihydroxyphenylo)-methylophosphonic acid with 4 mg/dm(3) Zn2+ and 2 mg/dm(3) phtalic anhydride and composition No VII, containing 50 mg/dm(3) 1,4-phenylobis-(amino, ethylbisphosphonic) acid, fulfilled international standards for inhibitor protection of industrial cooling water systems within 240 hours exposure time. Those inhibitor mixtures decrease corrosion rate of St3 steel in model water up to 0,03 mm/year and 0,01 mm/year while the deposition rate reaches the level of 0,79 g/(m(2).day) and 1,43 g/(m(2).day).