Corrosion Polarization Curves Research Articles

Unraveling the crucial contribution of additive chromate to efficient and stable alkaline seawater oxidation on Ni-based layered double hydroxides

Seawater electrolysis to generate hydrogen offers a clean, green, and sustainable solution for new energy. However, the catalytic activity and durability of anodic catalysts are plagued by the corrosion and competitive oxidation reactions of chloride in high concentrations. In this study, we find that the additive CrO42− anions in the electrolyte can not only promote the formation and stabilization of the metal oxyhydroxide active phase but also greatly mitigate the adverse effect of Cl− on the anode. Linear sweep voltammetry, accelerated corrosion experiments, corrosion polarization curves, and charge transfer resistance results indicate that the addition of CrO42− distinctly improves oxygen evolution reaction (OER) kinetics and corrosion resistance in alkaline seawater electrolytes. Especially, the introduction of CrO42− even in the highly concentrated NaCl (2.5 M) electrolyte prolongs the durability of NiFe-LDH to almost five times the case without CrO42−. Density functional theory calculations also reveal that the adsorption of CrO42− can tune the electronic configuration of active sites of metal oxyhydroxides, enhance conductivity, and optimize the intermediate adsorption energies. This anionic additive strategy can give a better enlightenment for the development of efficient and stable oxygen evolution reactions for seawater electrolysis.

The Effect of Heat Treatment on the Corrosion Resistance of Fe-Based Amorphous Alloy Coating Prepared by High Velocity Oxygen Fuel Method.

In this study, Fe40Cr19Mo18C15B8 amorphous coatings were prepared using high velocity oxygen fuel (HVOF) technology. Different temperatures were used in the heat treatment (600 °C, 650 °C, and 700 °C) and the annealed coatings were analyzed by DSC, SEM, TEM, and XRD. XRD and DSC results showed that the coating started to form a crystalline structure after annealing at 650 °C. From the SEM observation, it can be found that when the annealing temperature of the Fe-based amorphous alloy coating reached 700 °C, the surface morphology of the coating became relatively flat. TEM observation showed that when the annealing temperature of the Fe-based amorphous alloy coating was 700 °C, crystal grains in the coating recrystallized with a grain size of 5–20 nm. SAED analysis showed that the precipitated carbide phase was M23C6 phase with different crystal orientations (M = Fe, Cr, Mo). Finally, the corrosion polarization curve showed that the corrosion current density of the coating after annealing only increased by 9.13 μA/cm2, which indicated that the coating after annealing treatment still had excellent corrosion resistance. It also proved that the Fe-based amorphous alloy coating can be used in high-temperature environments. XPS analysis showed that after annealing FeO and Fe2O3 oxide components increased, and the formation of a large number of crystals in the coating resulted in a decrease in corrosion resistance.

Study on the corrosion mechanism of the oxide scale on hot rolled steel in an atmospheric environment

Purpose The purpose of this paper is to understand the process of failure of scale and the corrosion resistance of scale to the substrate in an atmospheric environment. Design/methodology/approach The corrosion behaviour of X65 pipeline steel with different types of oxide scale was analysed using the natural environment exposure corrosion test, scanning electron microscopy analysis, electrochemical corrosion polarization curve test and other methods in a warehouse environment. Findings The results of this research show that one type of oxide scale, which is rough, has an uneven microstructure, and exhibits weak adhesion to the matrix, does not protect the substrate from corrosion. Conversely, the uniform, dense oxide scale, which exhibits strong adhesion to the matrix, provides effective protection to the steel. However, as the corrosion develops, the corrosion rate of the substrate tends to accelerate, especially when the structure of the oxide scale is damaged to a certain extent. Originality/value The corrosion mechanism of the oxide scale on hot rolled steel in an atmospheric environment has been proposed.

Characteristics of Poly(3,4-ethylenedioxythiophene) Modified Stainless Steel as Anode in Air-Cathode Microbial Fuel Cells

Poly(3,4-ethylenedioxythiophene) (PEDOT) was electrochemically polymerized to in situ modify stainless steel (SS) plate electrode to improve its microbial bioelectrocatalytic activity as high-performance anode in microbial fuel cells. After modification, the surface of the electrode became rougher and showed better wettability. The electrochemical characteristics of PEDOT modified SS (PEDOT/SS) and bare SS electrodes were studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel corrosion polarization curves, respectively. It has been demonstrated that PEDOT modification could increase electrode capacitance and reduce electron transfer resistances. Compared with untreated SS, PEDOT/SS electrode showed better anticorrosion property as well. The modified anode produced a maximum power density of 608.6 mW/m2, which was about 6 times higher than bare SS anode. These results indicate that PEDOT treatment is an efficient method for SS to improve its performance as anode in MFCs.

Effect of electromagnetic and ultrasonic cast rolling on microstructure and properties of 1050 aluminum substrate for presensitized plate

The 1050 aluminum alloy strip was prepared by means of electromagnetic and ultrasonic cast rolling on the modified asymmetric twin roll caster, and then the aluminum substrate for presensitized plate was prepared through cold rolling and annealing. The effects of electromagnetic and ultrasonic cast rolling on microstructure, mechanical properties, surface roughness and electrolytic corrosion properties of 1050 aluminum substrate were studied. The results show that electromagnetic and ultrasonic cast rolling can decrease the average crystallite size of aluminum substrate by 5 μm, increase the crystal boundaries with uniform distribution, and make the second-phase particles with smaller size distributed dispersively in the substrate, meanwhile, it can increase the tensile strength, elongation and micro-hardness by 4.58%, 9.85% and HV 2, respectively, reduce the surface roughness, make the surface appearance more even, electrolytic corrosion polarization curve of aluminum substrate more smooth and the surface corrosion pits with regular shape more dispersive.

Investigating the microstructure and mechanical behaviors of DLC films on AISI52100 bearing steel surface fabricated by plasma immersion ion implantation and deposition

The microstructure and mechanical properties of diamond-like carbon (DLC) films fabricated on an AISI52100 bearing steel substrate surface by plasma immersion ion implantation and deposition (PIIID) were studied. Atomic force microscope (AFM) observation reveals that the DLC film has an extremely smooth surface, and high uniformity and efficiency of space filling over large areas. Raman spectroscopy analysis indicates that DLC films are mainly constituted by amorphous and crystalline phases, with a variable ratio of sp2/sp3 carbon bonds, and sp3 bond content of more than 10%. The maximum nanohardness and elastic modulus of the DLC film are 40GPa and 430GPa, and increase by 263.6% and 95.5%, respectively. The friction and wear results exhibit that the friction coefficient against an AISI52100 steel ball decreases from 0.87 to 0.20. The corrosion polarization curves in a 3.5% saturated NaCl solution shows that the corrosion resistance of DLC/AISI52100 samples is much better than that of bearing steel substrate. Compared with the bare bearing steel, the surface mechanical property of the DLC/AISI52100 sample is improved significantly.

Corrosion Resistance of KH-550 and KH-567 Composite Silane Films on Cast Aluminum Alloy

The silane films are fabricated by dipping cast aluminum alloy in silane solution, then curing films. The corrosion resistance of single silane film, composite silane film is compared with phosphating film through acid dropping test, salt water immersion test and electrochemical impedance test (EIS), the results shows that the silane films are obviously superior to the phosphating films in terms of the corrosion resistance of acid solution and neutral salt solution, particularly the corrosion resistance of composite silane films is much better than sigle silane films; corrosion polarization curves show that the corrosion tendency of KH550+KH567 composite silane film is minimum, corrosion rate is yet minimal, corrosion process of this silane films is controled by diffusion step. The corrosion process of uncoated aluminum substrate, KH550 silane films, phosphating films are controlled by electrochemical step. The impedance of phosphate films are lower than the silane films. Appropriate silane treatment can effectively improve adhesion between the coating and the Al substrate. The adhesion between silane film and paint film is firmer than the phosphate film, so silane film is an excellent replacement to phosphate film for painting pre-treatment.

Investigating the Mechanical Property and Rolling Contact Fatigue Life of Diamond-Like Carbon Films on Bearing Steel

Microstructure and properties of plasma immersion ion implantation and deposition diamond-like carbon (DLC) films on bearing steel substrate were studied. Raman spectroscopy analysis indicates that PIII&D DLC consists of a mixture of amorphous and crystalline phases, with a variable ratio of sp2/sp3 carbon bonds, and the sp3 bonds content more than 10%. The nanohardness (H) and the elastic modulus (E) of DLC films measurement indicate that the maximum H (E) value is 40GPa (430GPa). The corrosion polarization curves prove that the corrosion resistance of DLC samples is much better than that of substrate. The friction and wear behaviors and rolling contact fatigue (RCF) life of these samples show that the friction coefficient decrease from 0.87 to 0.2; the L10 , L50 , La and L life of treated sample increases by 9.1, 3.2, 2.5 and 2.4 times, respectively. The RCF life scatter extent of treated samples is improved significantly.

Magnetic separation of kaolin clay with amorphous ferromagnetic fiber

Approximately 2-3% Fe 2 O 3 as limo nite is contained in kaolin clay (Al 2 O 3 .2SiO 2 . 2H 2 O) in Suzhou, China. In this paper three kinds of amorphous ferromagnetic fibers were chosen as media in high extraction magnetic filtration (HEMF) for kaolin clay: 1. Fe 63 Ni 15 Si 7 B 15 ; 2. Fe 75 Cr 5 P 13 C 7 ; 3. Fe 73 Cr 7 P 13 C 7 ;. The amorphous ferromagnetic fiber should possess the properties of noncorrosion and produce a high magnetic field gradient in an external field. In this article, corrosion-polarization curves, HEMF efficiencies of three sorts of amorphous fiber and the effect of width of fibers on HEMF in various external fields are given. Evidently the efficiency of extraction magnetic filtration of narrow fibers is better than those of the wider one. The amorphous ferromagnetic fibers of Fe 75 Cr 5 P 13 C 7 (width about 0.2 mm) have the best separation effect. This medium can reduce the Fe2O 3 content from 2.01 wt% (crude ore slurry ) to 0.70 wt%.