Effect of Cu2+ on Corrosion Behavior of A106B Carbon Steel and 304L Stainless Steels in Seawater

The corrosion behaviors of A106B carbon steel and 304L stainless steel (SS) in seawater with different Cu2+ concentrations were studied by the immersion test and the potentiodynamic polarization test. The results showed that with the increasing Cu2+ concentration, the mass lot rates of A106B and 304L SS all increased in the immersion test, and compared with A106B, the mass lot rates of 304L SS were all smaller. In the potentiodynamic polarization test, following the concentration of Cu2+ increased, the corrosion potential of A106B firstly shifted negatively; then, when Cu2+ increased to 100 ppm, the polarization curve moved to the upper right direction; namely, both the corrosion potential and corrosion electrical density increased. The corrosion potential of 304L SS increased with the increasing Cu2+, and the passive region was reduced; the pitting sensitivity improved.

Effects of H2O2 and temperature on electrolytic pickling of austenitic stainless steel 304L in Na2SO4 solution

The effects of H2O2 solution addition and temperature on electrolytic pickling via an Na2SO4 solution to eliminate metal oxide layers from annealed 304L stainless steel were investigated by means of polarization. The experimental conditions involved a pure 190 kg × m-3 Na2SO4 solution and a mixture of 190 kg × m-3 Na2SO4 + 10 kg × m-3 H2O2 at 298, 318 and 333 K and pH 4. It was found that the addition of a 10 kg × m-3 H2O2 solution to a 190 kg × m-3 Na2SO4 solution and an increase in temperature resulted in a decrease in the passive region of the polarization curves. Results from SEM images, XRD patterns and root-mean-square roughness showed that the surface of the annealed 304L stainless steel was smoother and fewer remaining oxide scales were found when pickling in 190 kg × m-3 Na2SO4 + 10 kg × m-3 H2O2 solution. However, no effects on the pickling time at 298, 318 and 333 K through the addition of 10 kg × m-3 H2O2 solution to the 190 kg × m-3 Na2SO4 solution and the temperature were observed.

Effects of H2O2 and temperature on electrolytic pickling of austenitic stainless steel 304L in Na2SO4 solution

The effects of H2O2 solution addition and temperature on electrolytic pickling via Na2SO4 solution to eliminate the metal oxide layers of an annealed 304L stainless steel were investigated by polarization technique. The experimental conditions involved a pure 190 kg × m-3 Na2SO4 solution and a mixture of 190 kg × m-3 Na2SO4+ 10 kg × m-3 H2O2at 298, 318 and 333 K and pH 4. It was found that the addition of a 10 kg × m-3 H2O2 solution in 190 kg × m-3 Na2SO4 solution and an increase in temperature resulted in a decrease in the passive region of the polarization curves. The results from the SEM images, the XRD patterns and root-meansquare roughness showed that the surface of the annealed 304L stainless steel was smoother and fewer remaining oxide scales was found when pickling in 190 kg × m-3 Na2SO4 + 10 kg × m-3 H2O2 solution. However, no effects of the addition of 10 kg × m-3 H2O2 solution in 190 kg × m-3 Na2SO4 solution and temperature on pickling time at 298, 318 and 333 K were observed.

Effects of Chloride Ions and Nitrate Ions on the Anodic Dissolution of Iron in Sulfuric Acid Solution

In this paper, the flow injection (FI) technique combined with a partially-closed electrode (PCE) was used to manipulate the physicochemical microenvironment at the electrode/electrolyte interface so as to study the effects of chloride ions (Cl− ions) and nitrate ions (NO3− ions) on the anodic dissolution of the Fe/0.5 mol dm−3 H2SO4 system. The anodic dissolution is modified by injecting various composition-containing solutions into the vicinity of the PCE, and then, the electrodissolution processes are analyzed by comparing the j–t curves before and after the injections. At the initial stage of the passive region, it is found that NO3− ions promote the anodic dissolution of iron by creating more active sites on the surface of the electrode when CNO3−/CCl− = 1:1; however, they inhibit the anodic dissolution by making the film more compact for the strong oxidized characteristics of NO3− ions when CNO3−/CCl− = 10:1.

Investigating of Erosion-Corrosion Behavior of Carbon Steel in Egyptian Crude Oil-Water Mixture Using Electrochemical Method

An in-situ electrochemical polarization study was used to investigate the erosion-corrosion (E-C) behavior of C-steel in Egyptian crude oil-water mixture (ECWM) under mimetic different conditions. The anodic polarization responses for C-steel in ECWM are recognized active-passive region. Flow rate, sand particles and temperature increased the E-C rate. Disintegration rate to erosion rate proportion (E/C) was calculated and talked about.

Some peculiarities of the anodic behavior of Co2Si electrode in sulphuric acid solution

The effect of anodic film formation conditions on the electrochemical behavior of Co2Si electrode in 0.5 M H2SO4 has been studied. It was shown that the rate of passive dissolution of Co2Si is only moderately greater than that of CoSi2 provided the Co2Si electrode passes through the active dissolution region very quickly. From the current decay curves at E = const, it was deduced that in the middle part of the passive region the oxide film on Co2Si grows according to near logarithmic law. Impedance spectra obtained in measurements at different initial electrode potentials were analyzed.

Technical Note: Suppression of Anodic Kinetics of Stainless Steels During Biofilm Development in Natural Seawater

The anodic kinetics of three stainless steels, viz. UNS S31600, S44660, and N08367, in gently flowing natural seawater was investigated. Potentiodynamic anodic polarization showed two distinct passive regimes emerging with biofilm development. A dramatic decrease of anodic current densities (p < 10−4) was recorded in the lower passive region near the ennobled open-circuit potential, accompanied by an increase of the breakdown potential by over 0.2 V for Alloy S31600. However, significant broadening of the transpassive region was observed on all the three alloys tested. Further, for Alloys S44660 and N08367, the second passive region was altered during biofilm growth, which resulted in enhanced peak current densities. These seemingly undesired effects, nonetheless, were detected far beyond the domain of practical significance. Potentiostatic current-time curves for Alloy N08367 further confirmed the suppression of anodic kinetics in the lower passive region. Evans diagrams constructed from actual polarization curves provided fundamentally important insights that passivity promotion can be independent of microbially enhanced cathodic kinetics.

Effect of pyrite on the electrochemical behavior of chalcopyrite at different potentials in pH 1.8 H2SO4

Chalcopyrite is the most abundant, but also one of the most refractory, copper sources. One way to enhance chalcopyrite’s electrochemical dissolution is by mixing it with pyrite. To understand how and to what extent pyrite affects chalcopyrite’s electrochemical dissolution at different potentials, the electrochemical behaviors of chalcopyrite, pyrite, and chalcopyrite–pyrite couples in pH 1.8 H2SO4 were studied by potentiodynamic and electrochemical impedance spectroscopy. Potentiodynamic curves showed their different electrochemical reaction states and electrode surface characteristics. From open-circuit potential to 470 mV (vs saturated calomel electrode), chalcopyrite–pyrite was passivated with Cu1− xFe1− yS2 [Formula: see text]; from 470 to 580 mV, trans-passive dissolution occurred, and in the passive region, Cu1− xFe1− yS2 transformed into Cu1− x− zS2; from 580 to 700 mV was an active region; and a pseudo-passive region was formed with CuS when the potential was above 700 mV. The smaller charge transfer resistance and passive resistance, as well as the smaller inductive relaxation, revealed how and to what extent the coupled pyrite accelerated the electrochemical dissolution of chalcopyrite.

The impact of rotational speed and water volume on textile translational motion in a front-loading washer

Textile motion in a front-loading washer has been characterized via video capturing, and a processing system developed based on image geometric moment. Textile motion significantly contributes to the mass transfer of the wash solution in porous materials, particularly in the radial direction (perpendicular to the rotational axis of the inner drum). In this paper, the velocity profiles and residence time distributions of tracer textiles have been investigated to characterize the textile dynamics in a front-loading washer. The results show that the textile motion varies significantly with the water volume and rotational speed, and that the motion path follows certain patterns. Two regions are observed in the velocity plots: a passive region where the textile moves up with low velocity and an active region where the textile falls down with relatively high speed. A stagnant area in the residence time profile is observed. This corresponds to the passive region in the velocity profile. The stagnant area affects the mechanical action, thus influencing washing efficiency and textile performance. The findings on textile dynamics will help in the development of better front-loading washers.

Electrochemical behavior of tantalum in potassium hydroxide solutions

The electrochemical behavior of tantalum in various concentrations of KOH solutions (0.1 M - 10 M), was investigated using the evolution of the open circuit potential in time, cyclic voltammetry and ellipsometric measurements. Depending on KOH concentrations, the open circuit potential measurements have shown three distinct behaviors concerning oxide film formation on the electrode surface and its dissolution. The cyclic voltammetry measurements were performed in various potential ranges, from -1.4 to 8 V, different concentrations of KOH solutions (0.1-10 M) and sweep rates ranging from 0.005 V/s to 1 V/s. In the passive region, very stable passive films were formed, which reduction has not been possible during cathodic polarization even at highly concentrated KOH solutions. In the trans-passive region, the very strong peak at 1.65 V was monitored, which nature and chemical composition is still not well known.