Abstract
The effectiveness of two type corrosion inhibitors, such as chromate-polyphosphate type (inhibitor A) and zinc-polyphosphate type (inhibitor B) in cooling water has been studied. The inhibitor A is more effective than B for mild steel in water. Threshold concentrations of A and B under test condition were 30-50ppm and 70-100ppm respectively. Suitable pH-ranges for the inhibitors were 4-9 and 5-7 respectively. The inhibitor A shows good corrosion inhibition for mild steel in water containing 0-500ppm of SO2-4 or Cl-, but the efficiency of the inhibitor B decreases with the increase of concentrations of these anions.
