Corrosion Resistance Of Low Alloy Steel Research Articles

Effect of tin on the corrosion behavior of low-alloy steel in an acid chloride solution

This study examined the effect of Sn addition ranging from 0 to 0.1 wt.% on the electrochemical properties of low-alloy steel using electrochemical techniques in an acid chloride solution and surface analysis techniques. The potentiodynamic test showed the active corrosion behavior of all specimens and the corrosion rate decreased with increasing Sn addition. EIS showed that the Sn-containing steels had higher rust layer resistance. These results confirmed that the interaction of Sn with Cu and Sb improves the corrosion resistance of low-alloy steel due to the formation of the continuous tin oxide, copper oxide and antimony oxide layer.

Effects of copper on the corrosion properties of low-alloy steel in an acid-chloride environment

The influence of Cu addition on the corrosion resistance of low-alloy steel in an acid-chloride solution was investigated by electrochemical methods, such as potentiodynamic polarization tests and an electrochemical impedance spectroscopy (EIS). The XPS analysis of the corroded surfaces indicated the formation of protective Cu2O and Cu(OH)2 layers on the surface. The formation of Cu products on the surface reduced the uniform corrosion rate of the steel, but promoted localized corrosion due to the galvanic interaction between the covered areas of copper oxide/hydroxide and the uncovered areas on the surface of steel.

Effects of modifying trace components on petroleum pipeline corrosion resistance

A study has been made on the effects of modifying additives on the corrosion resistance of low-alloy steel: rare-earth, alkaline-earth, and zirconium additives. Optimal concentrations have been determined for cerium, yttrium, calcium, barium, and zirconium in steel that provide good corrosion resistance. Models have been derived for engineering and forecasting purposes as regards the working life of welded petroleum pipelines.

RETRACTED: Mechanical properties and corrosion resistance of low-alloy steels in atmospheric conditions containing chloride

The corrosion resistance (weight loss) and mechanical properties (i.e., yield strength, ultimate tensile strength, and elongation) of four newly developed low-alloy steels (LAS) were compared with a weathering steel (Acr-Ten A) and a carbon steel (SS400) using a laboratoryaccelerated test that involved cyclic wet/dry conditions in a chloride environment (5 wt.% NaCl). The new LAS were designated 1604A, 1604B, 1605A, and 1605B. After 72 cycles of cyclic corrosion tests, the change in mechanical properties by corrosion was the least for SS400, Acr-Ten A was second, and effects of corrosion on the mechanical properties of the other four low-alloy steels were similar. The susceptibility of the steels to corrosion based on their weight loss was the most for SS400, and the least for 1605A and 1605B. In addition, it was found that the corrosion potentials of low-alloy steels are more active prior to accelerated corrosion tests than after the accelerated test, and the corrosion tendency of the six steels immersed in 3.5 wt.% NaCl solutions after 72 cycles of accelerated corrosion tests was the least for 1605A and 1605B because the corrosion potentials were higher than other steels. The rust characteristics observed by SEM and analyzed by FTIR and EPMA indicated that most of the rust layers on the test steels were composed of a loose outer rust layer and a dense inner rust layer. The outer rust layer of each steel was composed of -FeOOH,-FeOOH, magnetite (Fe3O4), H2O, and amorphous ferric oxyhydroxide (FeOx(OH)3 − 2x, x = 0 to 1), while the inner rust layer was composed mainly of Fe3O4 with a little -FeOOH. In addition, it was apparent that the copper and chromium alloying additions were enriched, respectively, at the rust-layer/substrate interface and in the rust layers. Finally, combining the results of the accelerated tests, the rust layer analysis, and the corrosion potential measurements showed that low-alloy steels, such as 1605A and 1605B, have better weathering steel properties than Acr-Ten A for use in the humid and salty weather. © 2005 Elsevier B.V. All rights reserved.

Reanalysis of Thickness Loss Data for Weathering Steel

The current ASTM Standard Guide G101 has a method for estimating the atmospheric corrosion resistance of low-alloy steels from the content of five elements: Cu, Ni, Cr, Si, and P. The ASTM method was developed by fitting a quadratic model to thickness loss data from specimens that were made from 270 different steel compositions and were exposed to the atmosphere for 15.5 years. The quadratic structure resulted in a model that provides an irrational measure of the effect of the most important alloying element. Additionally, the use of the correlation coefficient as the single criterion for selecting predictor variables led to inaccurate coefficients. The reanalysis of the writers, using multiple criteria for selecting the best predictor variables, yields more accurate coefficients and a level of explained variance of nearly 80%. While the multiple criteria analysis of the writers does not sacrifice prediction accuracy to achieve rationality, the problem inherent to the quadratic model cannot be overcome altogether in low-alloy steels containing more than about 0.40% copper. The corrosion index of Guide 101 should not be used to decide whether a low-alloy steel qualifies as a weathering steel.

Estimation of atmospheric corrosion of high-strength, low-alloy steels

This data analysis was undertaken to investigate the weatherability of steels whose compositions do not fall in the range of ASTM Standard G101, Estimating the Atmospheric Corrosion Resistance of Low-Alloy Steels. This standard was developed to estimate the corrosion resistance of low-alloy weathering steels from chemical composition data and from actual atmospheric exposure tests. Thus, the Legault-Leckie equation, as well as similar equations for corrosion losses in the industrial environment used in the ASTMG101 Standard, cannot be used to estimate the corrosion losses for steels with concentrations of alloying elements beyond the data limits. Power-law-based equations such as those presented here estimate corrosion losses much better and are more appropriate for predicting the atmospheric corrosion loss of steels.

Atmospheric Corrosion of Steels

The effect of additional elements in low-alloy steel on the protective rust layer has been discussed from the view point of atmospheric corrosion.The rust layer of corrosion resistant low-alloy steel is made up of two layers, the outer one which is α or γ FeOOH and the inner one which is amorphous or very fine spinel type oxide (Fe3O4).The inner layer is supposed to play an important role in the corrosion resistance of low-alloy steels in atmosphere.The method of detecting the above-mentioned dense amorphous oxide layer is presented, and the mechanism of its formation is also discussed.