الفهرس يوجد فقط 14 صفحة متاحة للعرض العام
 |  | from | 200 |  |  |
| | | from | 200 | | |
المستخلص
Potential- .time curves are constructed for the steel electrode in naturally aerated Ca (OHh solutions, simulating the corrosion behavior in concrete. cr and SO/- ions cause the destruction of passivity and initiation of pitting corrosion. The rates of oxide film growth by Ca(OH)’2 and oxide film destruction by cr and SO/ ions follow a direct logarithmic law as evident from the linear relationships between the open circuit potential and the logarithm of immersion time. chromate, phospha~e, nitrite, tungstate and molybdate ions inhibit the pitting corrosion of steel by cr ions. In the presence of these inhibitive anions, the rate of oxide film healing and/or thickehing increases with their concentrations In presence of constant amons concentratIOn, theIr mhlbltIOn efficIency mcreases tn the order :
(weak) CrO/ < HPO/- < N02’ < WO/- < MoO/- (strong).
(2) The pitting corrosion current of reinforcing steel is measured under natural corrosion conditions using an H-divided cell in Ca(OH)2 in presence of cr as aggressive ions and CrO/-, HPO/-, N02’, WO/’, M0042- as inhibiting anions. The corrosion current starts to flow after an induction period which depends on solution composition (concentration, pH, concentration of cr ions and presence or absence of inhibiting anions). The limiting corrosion currents increase with increasing the cr ion concentration and decrease with decreasing the p~ and inhibiting Ions concentration. The inhibition efficiency of the studied inhibiting Ions decreases in the same order: Cr042- > HPO/- > N02’ > W042- > M0042’, and depends on the way by which the inhibitor is added to the solution.