New N-substituted 1-aminomethylenebisphosphonic acids as corrosion and scale inhibitors for water systems

Investigations under corrosion inhibition of carbon steel and precipitation of deposits in model water containing compounds of N-substituted 1-aminomethylenephosphonic acids was performed. The best corrosion efficiency, especially with low concentration in water (up to 20 mg/dm(3)), was achieved for 3,4-dicarboxyphenylaminomethylenebisphosphonic acid, which in potentiodynamic method reached 90% and in gravimetric method 82%, while corrosion rate was 2,6 mpy. This compound exhibits also advantageous results in prevention of CaCO3 deposit formation in water when its concentration is above 10 mg/dm(3). Potentiodynamic measurements revealed relatively good anticorrosive properties for the 4-hydroxyphenyl- and 3-carboxyphenyl-aminomethylenebisphosphonic acids, especially for their higher concentration in water.