Protection Of Cooling Water System In Motors Cars From corrosion using Sodium Nitrite and Sodium hexametaphosphate

Abstract

This research is included the investigation of electrochemical behaviour of Carbon-
Steel in natural aerated solution of cooling system for motor cars and performance of
sodium nitrite (SN) and sodium hexametaphosphate (SHMP) inhibitors blend for
inhibiting of such corrosion process under controlled conditions of mass transfer . To
achieved such control , under turbulent flow a rotating cylinder electrode ( R.C.E. )
system was designed to provide quantified hydrodynamics .
Potentiostatic polarization measurements under isothermal conditions were carried
out at ( 313 , 323 , 333 , 343 , 353 , 363 and 373 ) K by using uninhibited solution and
flow rates of ( 100 , 200 , 300 and 400 ) r.p.m. at each temperature . Corresponding
experiments for inhibited solution under the same conditions .
The results show that the limiting current density is increased with increasing the
temperature range and flow rate in uninhibited and inhibited solution . Also , the
corrosion potentials are generally shifted to the more positive direction with
increasing temperature and flow rate , whereas such potentials are shifted in less positive direction by using mixture from inhibitors . Increasing in limiting current
density (iL) with rate the rotation is obey Levich equation . The interpretation that it is
introduced in this study about the corrosion potential in uninhibited solution are
independence on the theory of mixed potential .
The mechanism of inhibition by using these inhibitors have been shown and
discussed .