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The weather in the Arabian Gulf region constitutes an environment that is corrosive to carbon steel. In the Gulf region, atmospheric corrosion is aggravated further by the high salinity of Gulf sea‐water. In addition, sulphur dioxide and deposits from combustion products tend to make the atmosphere in the Gulf region even more corrosive. Various inhibitors are reported in the literature that can help in the prevention of metal corrosion in aqueous environments. Among these, sodium dihydrogen orthophosphate, sodium benzoate, sodium nitrite and sodium nitrate were obtained and the effectiveness of certain corrosion inhibitors on carbon steel specimens was examined in a simulated atmospheric corrosion environment containing 2% NaCl and 1% Na₂SO₄ with various inhibitor concentrations. Test specimens were prepared from locally produced carbon steel reinforcing bars. It was found as a result of the test programme that treatment of the steel with 10 or 100mM sodium dihydrogen orthophosphate for one day at room temperature resulted in the best inhibition of corrosion. The results also demonstrated that inhibitors such as sodium benzoate and sodium nitrite were only similarly effective, as was sodium nitrate. Plans further study to examine the inhibition performance of sodium dihydrogen orthophosphate under actual atmospheric conditions.

The purpose of this study was to evaluate the effectiveness of sodium dihydrogen orthophosphate as an inhibitor to slow down or prevent atmospheric corrosion of the local mild steel during storage in the Arabian Gulf region. In light of the results of some preliminary studies, sodium dihydrogen orthophosphate was selected for further evaluation against atmospheric corrosion of steel after it was applied at 10 mM concentration for 1 day at room temperature.

The purpose of this investigation was to study the effects of sodium hexametaphosphate and zinc sulfate on the corrosion control of rusted iron in reverse osmosis (RO) product water of seawater.

The synergistic effects and inhibition effects of corrosion inhibitors on rusted carbon steel were studied using the weight-loss method, electrochemical tests and surface analysis techniques.

The results indicated that sodium hexametaphosphate could partly suppress the corrosion of rusted steel, but zinc sulfate used alone had no inhibition effect. Hexametaphosphate and zinc sulfate showed a strong synergistic effect and the optimal ratio of two chemicals was 1:1. The inhibition efficiency appeared to increase with increasing inhibitor concentration and the ideal dosage of inhibitors was set at 20 mg/L, when chemical cost and inhibition efficiency were taken into account. Surface analysis results proved that this compound inhibitor could make the rust layer much more compact. The inhibitive mechanism was to combine with rust and form a protective film, which consisted of iron oxide, polyphosphate and Zn(OH)₂.

It was found that the compound inhibitor consisting of sodium hexametaphosphate and zinc sulfate had a good inhibitive effect on rusted iron in RO product water. The research results can provide theoretical guidelines for corrosion control of rusted pipes in power plants.

Two corrosion inhibitors for closed cooling water systems, nitrite-based and mixture of nitrite and molybdate corrosion inhibitor, are often compared to each other. This study aims to optimize these two inhibitors in terms of concentration and pH for carbon steel protection, with insights into the double layer structure on surface and its impact on corrosion inhibition.

Electrochemical analysis including electrochemical impedance spectroscopy and potentiodynamic test are carried out for quick assessment of corrosion inhibition efficiency and optimization, which is confirmed by immersion test and microscopic analysis. The electronic properties of the surface film are analyzed through Mott–Schottky method which provides new insights into the inhibition mechanism and the role of each component in mixture inhibitor.

Mixture of nitrite and molybdate is shown to present higher inhibition efficiency, owning to the double layer structure. Nitrite alone can form a protective surface film, whereas molybdate leads to an n-type semiconductive film with lower donor density, hence giving rise to a better inhibition effect.

Surface after inhibitor treatment has been carefully characterized to the microscopic scale, implying the effect of micro-structure, chemical composition and electronic properties on the corrosion resistance. Inorganic corrosion inhibitors can be tuned to provide higher efficiency by careful design of surface film structure and composition.

Almost every study on corrosion inhibitor applies such method for quick assessment of corrosion inhibition effect. Mott–Schottky test is one of electrochemical methods that reveals the electronic properties of the surface film. Previous works have studied the surface layer mainly through X-ray photoelectron spectroscopy. This study provides another insight into the surface film treated by nitrite and molybdate through Mott–Schottky analysis, and relates this structure to the corrosion inhibition effect based on multiple analysis including electrochemistry, microscopic characterization, thermodynamics and interface chemistry.