A36 Carbon Steel Research Articles

Analysis of the Electrochemical Noise for Localized Corrosion of Type A516-70 Carbon Steel

Abstract Fluctuations of the corrosion potential (Ecorr) and the corrosion current were analyzed in the time domain for type A516-70 carbon steel (UNS K02700) exposed to 0.5 M sodium bicarbonate (N...

Study on rust layers on steel in different marine corrosion zone

The Mossbauer spectra for corrosion products formed on A3 carbon steel and low alloy 16Mn steel exposed in the Chengdao sea area for 2 years by the electro-connected method were determined. The phase composition and content of the rust layers on the two steels in four marine corrosion zones were analyzed and studied. Although the phase composition of the two steels were different, their main phase was β-FeOOH. The different content of FeOOH and Fe3O4 in the rust layers illustrated that FeOOH in the inner rust layer participated in the cathodic process as an oxidant accelerating the corrosion rate of steel under wet/dry cycle condition. Moreover, for the alloy elements in 16Mn steel, the rust layers with simple composition and fine and close texture formed a good barrier layer lowering the corrosion rate of low alloy steel.

Crevice corrosion behavior of A516-70 carbon steel in solutions containing inhibitors and chloride ions

Fluctuations of the corrosion potential and current were analyzed in the time domain for type A516-70 carbon steel immersed in 0.5 M NaHCO 3 or 0.1% NaNO 2 solutions containing NaCl at various concentrations. The fluctuations of corrosion potential and current observed for pitting corrosion showed a pattern distinctly different from that for crevice corrosion of this type of carbon steel immersed in the solutions described. Sharp potential and current fluctuations with amplitudes approaching several millivolts and several tens of microamperes, respectively, were detected during the pitting process. The fluctuations of the potential produced during pitting occurred around the corrosion potential (−250 to −280 mV vs. SCE). As crevice corrosion proceeded in the solution containing 0.5M bicarbonate as inhibitor and chloride ions as aggressive ions, the corrosion potential slowly decreased from −250∼−280 mV to about −480 mV. The corrosion current increased simultaneously. Then the corrosion potential dropped sharply to around −760 mV and remained at this value, while the coupling current from working electrode 1 to working electrode 2 through the solution rapidly decreased. In the case of crevice corrosion on the carbon steel in the nitrite base solution, the chloride ions caused a drop of potential into the potential range of −370 to −470 mV. The potential then returned to the original corrosion potential for the dilute chloride solution, and remained in this potential range for the chloride solution of moderate concentration, or declined to the range of −530 to −570 mV due to the active crevice corrosion induced by the chloride ions at high concentration. The magnitude and number of the current fluctuations increased with the concentration of chloride ions. The time dependence of the corrosion potential and current provided information on the mechanisms of crevice corrosion and inhibitors.

Features of electrochemical noise generated during pitting of inhibited A516-70 carbon steel in chloride solutions

The features of electrochemical noise generated during pitting of A516-70 carbon steel in chloride solutions containing Na2CrO4 were investigated. Polarization curves showed that the threshold Cl− concentration in 0.01m Na2CrO4 solution to initiate pitting and the threshold CrO42− concentration in 0.1m NaCl solution to maintain passivation for A516-70 carbon steel were approximately 0.1m and 0.01m, respectively. Noise measurements indicated that above the critical Cl− concentration, the stochastic current fluctuations appeared after 5h of immersion, which was an indication of pit initiation. Increasing CrO42− concentration to 0.05m led to the production of symmetrical current spikes at the start of immersion. The noise pattern changed to frequent fluctuations with small amplitude during immersion. Noise analysis in the frequency domain showed that pitting initiation was characterized by the slope of the PSD plot approaching -2. Extending the immersion time decreased the pitting initiation rate, as indicated by the decreased PSD slope and increased PSD frequency.

Study on the corrosion peak of carbon steel in marine splash zone

This study determined that the range of the marine splash zone (MSZ) of China's Qingdao, Zhoushan, Xiamen, Zhanjiang harbour area was about 0–2.4 m above the mean high water level (MHWL) of the seawater; that the MSZ corrosion peak (MSZCP) was usually 0.6–1.2 m above the MHWL, and was caused by the large salt particle accumulation on the A3 carbon steel test sample surface and by the high frequency alternations of wet and dry environmental conditions around the samples.

Electrochemical Behavior of A516 Carbon Steel in Solutions Containing Hydrogen Sulfide

Abstract The electrochemical behavior of A516 grade 70 (UNS K02700) carbon steel with a ferrite-pearlite structure in acidic chloride (Cl−) solutions containing hydrogen sulfide (H2S) at 25°C was i...

Dilution in single pass arc welds

A study was conducted on dilution of single pass arc welds of type 308 stainless steel filler metal deposited onto A36 carbon steel by the plasma arc welding (PAW), gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and submerged are welding (SAW) processes. Knowledge of the arc and melting efficiency was used in a simple energy balance to develop an expression for dilution as a function of welding variables and thermophysical properties of the filler metal and substrate. Comparison of calculated and experimentally determined dilution values shows the approach provides reasonable predictions of dilution when the melting efficiency can be accurately predicted. The conditions under which such accuracy is obtained are discussed. A diagram is developed from the dilution equation which readily reveals the effect of processing parameters on dilution to aid in parameter optimization.

Electrochemical behavior of the simulated heat-affected zone of A516 carbon steel in H 2S solution

Electrochemical behavior of the simulated grain-coarsened heat-affected zone (HAZ) of A516 carbon steel in an H 2S containing acidic chloride solution was investigated by electrochemical impedance spectroscopy (EIS) measurement at open circuit potential at 25 °C. EIS measurement was made for the specimens, prepared with three different heat input conditions (15, 30 and 45 kJ.cm −1) by thermal simulation with a Gleeble machine, in the H 2S containing solution. The results show that the corrosion process of the simulated grain-coarsened HAZ can be divided into two stages regardless of the heat input condition. At an early stage, the impedance which is characterized by one large semicircle in the Nyquist plot increases with immersion time. At a later stage, the precipitation of sulfide film modifies the surface properties and leads to a variation in the EIS data by revealing a capacitive effect in the low frequency region. The polarization resistance initially increases with immersion time but then decreases gradually. Equivalent circuits containing two or three time constants are proposed to represent the corrosion processes at different stages.

Corrosion morphology of A516 carbon steel in H 2S solution

Corrosion morphology of A516 carbon steel in H 2S solution

Sodium Molybdate as a Corrosion Inhibitor of Mild Steel in Natural Waters Part 1: Flow Rate Effects

Abstract Sodium molybdate (Na2MoO4) has been proposed as a possible replacement for chromate-based corrosion inhibitors for steel. Although Na2MoO4 is used in industry, little characterization of its behavior in low-conductivity natural waters or under flowing conditions has been performed. Effects of flow rate and water treatment on ASTM A36 carbon steel (UNS K02600) in natural lake water has been examined by electrochemical impedance spectroscopy (EIS) using the rotating cylinder electrode technique. The corrosion behavior of A36 steel was found to be highly dependent upon flow rate in untreated natural water, but only moderately dependent upon flow rate in waters treated with Na2MoO4, as determined by alternating and direct current methods. The electrochemical impedance spectra of steel in natural water were corrupted by artifacts at frequencies of 100 Hz and above. These artifacts were exacerbated by the low conductivity of the natural water. The solution and polarization resistances were isolated in ...

Low Cycle Fatigue of Commercial Piping Steels in a BWR Primary Water Environment

This report summarizes results of a comprehensive experimental program on the low cycle fatigue behavior of commercial grade piping steels in a high-pressure, high-temperature, oxygenated water environment. A total of 110 specimens of special design were tested in a boiling water reactor (BWR) primary water environment (500°F, 1040 psig (or 260° C, ∼ 7 MPa). Four piping steels, in several different metallurgical conditions, were involved (Types-304 and –304L stainless steels, Inconel-600 and A-516 carbon steel). Companion tests, employing the same types of specimens, were conducted in 500° F (260° C) air. The results of this work confirm the adequacy of the current ASME Section III fatigue design curves to account for the effect of a BWR primary water environment on the low cycle fatigue behavior of the four materials tested.