Corrosion Behavior Of Low Alloy Steel Research Articles

Influence of Chromium on Corrosion Behavior of Low-alloy Steel in Cargo Oil Tank O2-CO2-SO2-H2S Wet Gas Environment

As international maritime organization (IMO) draft 289 was adopted to develop a low-alloy anti-corrosion steel for the deck of cargo oil tank and to understand corrosion mechanism, corrosion behavior of a low-alloy steel with chromium contents was studied in O2-CO2-SO2-H2S wet gas environment. Corrosion rate was measured, and the microstructure and morphology of corrosion product film were characterized by scanning electron microscopy (SEM). The phase and chemical composition of the corrosion product film were investigated by X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), respectively. The effect of misorientation distribution on corrosion resistance of steel was evaluated by electron backscattered diffraction (EBSD). The results showed that corrosion rate decreased with increasing chromium content in the low-alloy steel, and the corrosion type was general corrosion. The phenomenon of chromium enrichment was found in corrosion product film consisting of α-FeOOH, γ-FeOOH, sulphur, FeS2 and Fe1–x S. The increase of chromium content decreases the amount of high-angle grain boundaries, thus resulting in the improvement of corrosion resistance.

Corrosion behavior of low-alloy steel with martensite/ferrite microstructure at vapor-saturated CO2 and CO2-saturated brine conditions

The immersion experiment was carried out to study the corrosion behavior of low-alloy steel with martensite/ferrite microstructure at vapor-saturated CO2 and CO2-saturated brine conditions. The characteristics of corrosion behavior are investigated by the microstructure of tested steel, corrosion rate, corrosion phase, surface morphology and cross-section morphology. The results demonstrate that the microstructure of tested steel consists of tempered martensite and ferrite, and ferrite may dissolve preferentially in corrosion process. The corrosion products comprising of inner layer and outer layer at both vapor-saturated CO2 and CO2-saturated brine conditions are Cr-rich compound and FeCO3, respectively. The corrosion rate at vapor-saturated CO2 condition is tremendously lower than that at CO2-saturated brine condition. The corrosion rate and scale morphology show that the compact and dense outer layer plays an important role on corrosion resistance, although the inner layer appears firstly. Based on the results of this experiment, the underlying mechanisms of low-alloy steel with martensite/ferrite microstructure are proposed to illustrate carbon dioxide corrosion behavior.

Effect of chloride ions on the corrosion behavior of low-alloy steel containing copper and antimony in sulfuric acid solution

The influence of the addition of HCl on the corrosion behavior of low-alloy steel containing copper and antimony was investigated using electrochemical (potentiodynamic and potentiostatic polarization tests, and electrochemical impedance spectroscopy) and weight loss tests in a 1.6M H2SO4 solution with different concentrations of hydrochloric acid (0.00, 0.08, 0.15 and 0.20 M HCl) at 60 °C. The result showed that the corrosion rate decreased with increasing HCl by the formation of protective layers. SEM, EDS and XPS examinations of the corroded surfaces after the immersion test indicated that the corrosion production layer formed in the solution containing HCl was highly comprised of metallic Cu, Cu chloride and metallic (Fe, Cu, Sb) compounds. The corrosion resistance was improved by the Cu-enriched layer, in which chloride ions are an accelerator for cupric ion reduction during copper deposition. Furthermore, cuprous and antimonious chloride species are complex salts for cuprous ions adsorbed on the surface during copper deposition.

Corrosion Behavior of Low-Alloy Pipeline Steel with 1% Cr Under CO2 Condition

Carbon dioxide corrosion behavior of low-alloy pipeline steel with 1% Cr exposed to CO2-saturated solution was investigated by immersion experiment. SEM, EDX, TEM, EPMA and XRD were utilized to investigate the microstructure, corrosion morphologies, corrosion phases and elements distribution of corrosion scale. The results demonstrate that the microstructure of tested steel consists of ferrite and carbides. During the corrosion process, ferrite dissolves preferentially, leaving carbide particles behind. The residual carbide particles may promote the nucleation of FeCO3 crystal. The phase comprising of the inner layer is Cr compound, and the one of the outer layer is FeCO3. The formation process of corrosion scale can be illustrated as follows: Firstly, a thin scale consisting of thin inner layer and outer layer is formed, which represents poor corrosion resistance; then, the inner layer changes little, once it has been formed, and the outer layer becomes thick and compact, which demonstrates that a fine corrosion resistance is obtained. The chemical elements of chromium and molybdenum accumulate in the inner layer of corrosion scale. The corrosion behavior of low-alloy steel based on microstructure and morphology characterization is also discussed.

Influence of Inclusion on Corrosion Behavior of E36 Grade Low-alloy Steel in Cargo Oil Tank Bottom Plate Environment

Corrosion behavior of low-alloy steel was investigated in simulated cargo oil tank (COT) bottom plate service environment (10% NaCl solution, pH = 0.85). The corrosion behavior of inclusion was studied by in-situ scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). It was found that pitting corrosion was inclined to occur around the place where inclusions exist. After initial corrosion, an area of 10–20 μm in diameter was formed as a circinate cathode around the edge of inclusion. MnS inclusion dissolved in the simulated COT corrosion solution before low-alloy steel matrix, and pitting was formed at the place where MnS dissolved. TiO2 inclusion dissolved in the simulated COT corrosion solution after low-alloy steel matrix, and pitting was formed at the place where steel matrix dissolved. The corrosion tended to occur at the area where the curvature radius of inclusion is smaller. The size of round TiO2 inclusions had little influence on corrosion behavior in this certain environment.

Effect of W, Mo, and Ti on the Corrosion Behavior of Low-Alloy Steel in Sulfuric Acid

The effects of W (0.05 wt% W), Mo (0.05 wt% Mo), and Ti (0.05 wt% Ti) addition on the corrosion resistance of low-alloy steel used in flue gas desulfurization systems were examined using electrochemical measurements in a 10 wt% sulfuric acid (H2SO4) solution. The corrosion rate increased in the following order: W steel < Mo steel << Ti steel. The surface analysis indicated that the type and quantity of inclusions by steel are as follows: W steel (manganese sulfide [MnS]) < Mo steel (MnS, molybdenum disulfide [MoS2]) << Ti steel (MoS2, titanium sulfide [TiS]). The corrosion rate was influenced by sulfide inclusions in the steels. In particular, the corrosion rate of Ti-containing steel was the highest due to a large number of TiS inclusions formed during the steel manufacturing or corrosion processes.

Corrosion behavior of low-alloy steel containing 1% chromium in CO2 environments

Abstract Corrosion behavior of low-alloy steel containing 1% Cr (1Cr) with normalized (ferritic–pearlitic) and quenched-and-tempered (tempered martensitic) microstructures was investigated in CO 2 environments at 60 °C. The severe localized corrosion which was observed in N80 carbon steel, did not exist for 1Cr steel due to the formation of a compact and self-repairable Cr-rich scale. For 1Cr steel, the corrosion resistance with ferritic–pearlitic microstructure was better than that with tempered martensitic microstructure. An apparent corrosion scale spallation was observed on the surface of quenched-and-tempered 1Cr steel, while only slight scale spallation was seen for normalized 1Cr steel.

Investigations on the effect of chloride on the general corrosion behavior of low-alloy steels in oxygenated high-temperature water

This project focused on investigations on the effect of chloride contaminations on the general corrosion and crack initiation behavior of low-alloy steel (German reactor pressure vessel steel 22NiMoCr3 7) in oxygenated high-temperature water (HTW). Therefore, tests were performed in oxygenated HTW without chloride and at different chloride contamination levels up to 50 ppb. Chloride was added either permanently or temporarily to simulate a chloride transient during plant operation. During these tests, electrochemical noise (EN) and electrochemical impedance spectroscopy (EIS) measurements were performed to monitor the electrochemical behavior depending on the adjusted environment conditions, especially the effect of chloride on the degradation of low-alloy steel. After the tests, the specimens were examined macroscopically and microscopically. In addition, the oxide layer thickness was determined using the focused ion beam (FIB) technique and different surface analysis techniques as, e.g., TOF-SIMS were performed to analyze the composition of the oxide layer. A change of the corrosion behavior of the tested specimens was revealed by the applied electrochemical methods EN and EIS during high-temperature testing. In addition, the applied post-test investigations showed a decrease in the oxide layer thickness due to permanently increased chloride concentrations in the HTW. Temporary transients, however, did not cause a long-term memory effect as shown by both, the electrochemical and the metallographic post-test investigations.

Alloying Effect of Chromium on the Corrosion Behavior of Low-Alloy Steels

Alloying effect of Cr in the interaction with other elements in low alloy steel for corrosion resistance was designed and prepared. The corrosion behavior of the alloy immersed in mild acid­chloride solution (200 atomic ppm Cl and pH 4) at room temperature in an ambient condition has been studied by electrochemical laboratory tests (potentiodynamic polarization test, potentiostatic test, electrochemical impedance spectroscopy) and surface analyses (SEM, XPS). The results reveal that Cr addition improved the localized corrosion resistance by promoting the formation of beneficial Fe and Cu compounds on the protective films of 0.1 and 0.3mass% Cr steels. However, the over-alloying circumstance in 0.5mass% Cr steel caused the negative effect of Cr addition due to metal chloride-induced hydrolysis which accelerated the propagation of the localized corrosion. To summarize, 0.3mass% Cr addition was determined to be the optimum value for alloying to blank steel. [doi:10.2320/matertrans.M2013087]

Effect of tungsten on the corrosion behavior of sulfuric acid-resistant steels for flue gas desulfurization system

Flue gas desulfurization systems (FGDs) are operated in severely corrosive environments that cause sulfuric acid dew-point corrosion. The corrosion behavior of low-alloy steels was tested using electrochemical techniques (electrochemical impedance spectroscopy, potentiodynamic tests, potentiostatic tests), and the corrosion products were analyzed by scanning electron microscopy and X-ray photoelectron spectroscopy. The electrochemical results showed that alloying W with small amounts of Sb, Cu, and Co improves the corrosion resistance of steels. The results of surface analyses showed that the surface of the steels alloyed with W consisted of W oxides and higher amounts of Sb and Cu oxides. This suggests that the addition of W promotes the formation of a protective WO3 film, in addition to Sb2O5 and CuO films on the surface.

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.

Corrosion behavior of low-alloy steel in the presence of Desulfotomaculum sp.

The objective of this study was to determine the effect of sulfate-reducing Desulfotomaculum sp. bacteria isolated from a crude oil field on the corrosion of low-alloy steel. The corrosion rate and mechanism were determined with the use of Tafel slopes, mass loss method and electrochemical impedance spectroscopy (EIS). The formation of the biofilm and the corrosion products on the steel surface was determined with scanning electron microscopy (SEM) micrographs and energy dispersive X-ray spectra (EDS) analysis. It was observed from the Tafel plots that the corrosion potential exhibited a cathodic shift that verifies an increase in the corrosion rates. The semicircles tended to open at lower frequencies in the Nyquist plots which indicates the rupture of the protective film. The corrosion current density reached its maximum value at the 14th hour after the inoculation and decreased afterwards. This was attributed to the accumulation of corrosion products on the surface.

Effect of antimony on the corrosion behavior of low-alloy steel for flue gas desulfurization system

The alloying effect of Sb in a new low-alloy steel for the purpose of FGD materials was investigated by potentiodynamic polarization, linear polarization resistance measurement, electrochemical impedance spectroscopy (EIS) and weight loss measurements in an aggressive solution of 16.9 vol.% H 2SO 4 + 0.35 vol.% HCl (modified green death solution) at 60 °C, pH −0.3. All measurements confirmed the marked improvement in the corrosion behavior of the low-alloy steel via the addition of a small amount of Sb, particularly for the 0.10Sb steel. Pitting corrosion was detected by scanning electron microscopy (SEM) on the surface of blank steel and 0.05Sb steel, but not 0.10Sb steel, after weight loss measurements. X-ray photoelectron spectroscopy (XPS) analysis of the corroded surfaces after EIS and linear polarization measurements showed that the decrease in corrosion rates was due to the formation of a protective Sb 2O 5 oxide film on the surface of the Sb-containing steels. Moreover, the addition of 0.10% Sb stimulated the development of high corrosion inhibiting, Cu-containing compounds which further inhibited the anodic and cathodic reactions.

ケルビンプローブによる吸着・薄膜水下の低合金鋼の腐食挙動測定

ケルビンプローブによる吸着・薄膜水下の低合金鋼の腐食挙動測定

Kinetics of the Atmospheric Corrosion of Low-Alloy Steels in an Industrial Environment

Abstract It has been demonstrated that the natural atmospheric corrosion behavior of low-alloy steels in industrial environments can be accurately described by an equation of the form: ΔW = K tN. T...