Inhibitor composition for corrosion protection of steels in water systems based on polymers and inorganic salts

The inhibiting properties of various compositions of polyethylene glycol and some inorganic salts (Na 2 MO 4 and Na 2 WO 4 .2H 2 O) in respect to the corrosion of carbon steel in water environment have been studied using electrochemical polarization techniques, gravimetric measurements, electron microscopy (SEM) and metallography observations. As a model medium of non-treated water 0.1 N Na 2 SO 4 solution (pH = 6.7) is used. It is established that the composition of polyethylene glycol (molecular mass 1000) and Na 2 WO 4 .2H 2 O is the most efficient - the inhibition effect is up to 90%. It is shown that the inhibitor composition affects most significantly the anodic behaviour and susceptibility of the steel to passivation. The addition of the composition results in considerable decrease in the rate of anodic dissolution of the steel and increase of the width of the passive region as well as in lowering of the passivation current density. Formation of protective film of mixed oxide-adsorption nature on the steel surface in the presence of the inhibitor composition is suggested.