Corrosion Performance Of Steel Research Articles

Role of alkaline nitrites in the corrosion performance of steel in composite cements

The influence of alkaline nitrites on the inhibition of corrosion of steel in binary and ternary cement environments was tested. pH measurements carried out for binary and ternary cement extracts showed that the alkalinity of the cement was not affected by making use of binary and ternary cements. Gravimetric measurements showed that the decrease in the corrosion rate of steel in different systems follows the order: Ternary > (OPC + PSC) > (OPC + PPC) > (PPC + PSC). Potential–time studies indicated that the ability to maintain the passivity of steel in different systems also follows the order as above. Potentiodynamic polarisation studies for steel in binary and ternary cement environments showed the favourable influence of the presence of higher amounts of chlorides. Nitrites of sodium, potassium and calcium act as anodic inhibitors and they compete with chloride ions for the ferrous ions at the steel to form a film of ferric oxide. An efficiency as high as 91% is obtained for the ternary system containing 1% chloride and 0.5% nitrite. The degree of surface coverage showed a maximum value for the ternary system (>0.9) even in the presence of a higher amount of chloride thereby indicating the better performance of the system.

Effectiveness of fly ash activation on the corrosion performance of steel embedded in concrete

The use of fly ash to replace a portion of cement has resulted in significant savings in the cost of cement production. Fly ash blended cement concretes require a longer curing time and their early strength is low when compared with ordinary Portland cement (OPC) concrete. By adopting various activation techniques such as physical, thermal and chemical methods, hydration of fly ash blended cement concrete was accelerated and thereby improved the corrosion resistance of concrete. Concrete specimens prepared with 10, 20, 30 and 40% of activated fly ash replacement were evaluated for their open-circuit potential measurements, weight loss measurements, impedance measurements, linear polarisation measurements, water absorption test, rapid chloride ion penetration test and scanning electron microscopy test and the results were compared with those for OPC concrete without fly ash. All the studies confirmed that, up to a critical level of 20–30% replacement, activated fly ash cement improved the corrosion resistance properties of concrete. It was also confirmed that the chemical activation of fly ash yielded better results than the other methods of activation investigated in the current study.

Effect of Al alloying on corrosion performance of steel

To clarify some features of the atmospheric corrosion mechanism, the corrosion performance of Al bearing steels after wet/dry cyclic corrosion tests were studied by gravimetry, SEM, X-ray diffraction (XRD), potentiodynamic polarisation tests and electrochemical impedance spectra (EIS). The results showed that rusted Al bearing steel presented a better corrosion resistance than that of rusted plain carbon steel (Q235) in 0·3%NaCl (i.e. simulating a marine environment) solution; moreover, the corrosion resistance of Al bearing steel increased with increasing Al content. The formation of a spinel double oxide containing Al(FeAl2O4) in Al alloying steels was observed, which refined the structure of the inner rust layer, suppressed the anodic dissolution and accelerated the cathodic reduction. In addition, Al alloying increased the content of γ-FeOOH and decreased that of β-FeOOH. However, in NaHSO3 solution (i.e. simulating an industrial environment), the rust layer on Al bearing steel did not possess a protective ability, and the rust layer formed was not physically or chemically stable.

Corrosion performance of steel coated with co-polyamides and polyaniline

The corrosion performance of steel coated with co-polyamide polymers and polyaniline in neutral salt spray (NSS) and accelerated corrosion testing is presented. A coating of the nylon polymer on steel is not sufficient to prevent corrosion in a chloride medium, the underlying steel showing signs of corrosion after only three days in the NSS environment. Open-circuit potential measurements indicate the steel is corroding forming soluble ferrous and ferric oxy-complexes. Polyaniline by itself is also insufficient in inhibiting corrosion on steel. A synergy exists between an under-layer of polyaniline and a top layer of the nylon coating in minimizing corrosion.

Effect of H2S on corrosion in polluted waters: a review

The present article provides an overview of the effect of hydrogen sulphide (H2S) on corrosion in polluted waters, including sea, river, brackish, geothermal and sewage waters. H2S is a weak, reducing acid which originates from sulphide minerals by natural acidification and/or from sulphur – bearing, decaying organic matter by bacterial action. Human and industrial activities increase the generation of corrosive gases, dissolved in water: CO2, H2S and NH3. Carbon steel, stainless steel, aluminium alloys and copper base alloys are corroded by H2S, producing metallic, non-stable sulphide films. The H2S content in various waters, the electrode potential pH (Pourbaix) diagrams for Fe and Cu in H2S containing systems, and the electrochemical and corrosion performance of steel in oxygen depleted, H2S polluted waters, which indicate active corrosion behaviour, are presented and discussed.

Electrochemical studies on the corrosion performance of steel embedded in activated fly ash blended concrete

The use of fly ash to replace a portion of cement has resulted significant savings in the cost of cement production. Fly ash blended cement concretes require a longer curing time and their early strength is low when compared to ordinary Portland cement (OPC) concrete. By adopting various activation techniques such as physical, thermal and chemical methods, hydration of fly ash blended cement concrete was accelerated and thereby improved the corrosion-resistance of concrete. Concrete specimens prepared with 10–40% of activated fly ash replacement were evaluated for their open circuit potential measurements, weight loss measurements, impedance measurements, linear polarization measurements, water absorption test, rapid chloride ion penetration test and scanning electron microscopy (SEM) test and the results were compared with those for OPC concrete without fly ash. All the studies confirmed that up to a critical level of 20–30% replacement; activated fly ash cement improved the corrosion-resistance properties of concrete. It was also confirmed that the chemical activation of fly ash yielded better results than the other methods of activation investigated in this study.

Accelerated short-term techniques to evaluate the corrosion performance of steel in fly ash blended concrete

In this investigation, the influence of mineral admixture, namely fly ash (FA) on the corrosion performance of steel in mortar and concrete was studied and evaluated by some accelerated short-term techniques in sodium chloride solutions. Electrochemical techniques such as open circuit potential measurements and anodic polarization studies were carried out. An impressed voltage technique and macrocell corrosion study was also carried out to understand the optimum level of replacement of FA with better corrosion resistance properties. Results are compared with conventional gravimetric weight loss measurements. The alkalinity and the free chloride contents are estimated. The FA replacement levels namely 10%, 20%, 30% and 40% with respect to ordinary Portland cement (OPC) was chosen for the present study and the results are compared with OPC specimens without FA.

A new pozzolan for high performance cementitious materials

This paper presents results on the physical and chemical properties of metakaolinite, MK which is prepared by dehydroxylation of high quality kaolinite. The properties of Portland cement mortars blended with MK additions up to 50% are investigated. These properties are compressive strength, pore size distribution, resistance to the penetration of water and chloride ions and corrosion performance of steels embedded in the mortar. The optimum replacement of ordinary Portland cement (OPC) with MK to obtain high strength concrete is about 20%, but it is possible to use a higher percent in order to achieve the best durability properties and strength similar to the control mixture. There is a significant decrease in average pore size with an increase in MK replacement. Metakaolinite is able to bind chloride ions to produce Friedel's salt (SF), which can be considered as the main cause of the lower chloride penetration in portland cement mortars blended with MK addition. This chemical binding capacity was proved by XRD. In general, the test results indicate that the MK is a highly pozzolanic material and can be used as a supplementary cementing material in order to produce a high-performance concrete especially for use in aggressive environments. Such as, thawing salts and dew of the sea.

Resistencia a la corrosión atmosférica del recubrimiento Zn-10,2% Fe sobre chapa de acero. Comparación con el recubrimiento de zinc

Zn-10.2 % Fe galvanized coating versus hot galvanized coating over carbon steel corrosion performance has been studied. Different periods of atmospheric exposures in various Valencia Community sites, and salt spray accelerated test have been done. Carbon steel test samples have been used simultaneously in order to classify exposure atmosphere corrosivity, and environmental exposure atmosphere characteristics have been analyzed. Corrosion velocity versus environmental parameters has been obtained.