General Corrosion Resistance Research Articles

Microstructural evolution and corrosion behavior of Al25Ti25Ga25Be25 equi‐molar composition alloy

The microstructure of light element containing Al25Ti25Ga25Be25 equi‐molar composition alloy was investigated by X‐ray diffractometry and scanning electron microscopy, while the corrosion behavior was tested in 1 M sulfuric acid solution (H2SO4) at ambient temperature (298 K). The results show that the alloy displays good general corrosion resistance. The influence of the microstructure and morphology of the constituent phases is also evaluated.

Finite Element Modeling for Prediction of Stress – Strain at Several Feed Rates and Cutting Speeds for Titanium (Ti-6Al-4V) Alloy

Titanium (Ti-6Al-4V) alloy is a desirable material for the aircraft industry because of their excellent properties behaves of high specific strength, fracture resistant characteristics, lightweight and general corrosion resistance. This paper presents a study on a two-dimensional orthogonal cutting process by using a face-milling operation through ABAQUS/EXPLICIT finite-element software. Several tests were performed at various feed rates and cutting speeds while the depth of cut remains constant. The results led to the conclusion that the stress components at integration points (Von - Mises) and the equivalent strain (PEEQ) were increased with increasing the feed rate and cutting speed during the machining process.

Basic Electrochemical Behavior of Ti-7Cu Alloys for Medical Applications

The aim of this study was to investigate the e ects of two di erent treatments, as-cast setup and solution heat treatment, on the general electrochemical corrosion resistance of Ti 7Cu alloy samples immersed in a 0.9 wt% NaCl solution at 25 ◦C. The microstructure was examined by scanning electron microscopy and X-ray di ractometry. Corrosion behavior was tested by potentiodynamic polarization curves. Finer α′ martensite and Ti2Cu intermetallic particles were provided by casting and heat treated processes, respectively. The results indicated that only corrosion potential is signi cantly more noble in the heat treated sample, but other characteristics are only slightly di erent.

Structure and Corrosion Resistance of PEO Ceramic Coatings on AZ91D Mg Alloy Under Three Kinds of Power Modes

Power mode is one of the most important factors in the plasma electrolytic oxidation (PEO) technique, which greatly influences the structure and performances of the prepared ceramic coatings. The aim of this work was to investigate effects of three kinds of power modes (constant voltage (Mode 1), constant current (Mode 2), and constant power (Mode 3)) on the structure and corrosion resistance of the PEO ceramic coatings containing Ca and P on AZ91D Mg alloy. The phase composition, morphology, and the element distribution of the coatings was studied using X‐ray diffraction, scanning electron microscopy, and energy‐dispersive spectroscopy, respectively. The electrochemical impedance spectrum was measured to evaluate the structure and the corrosion resistance. The polarizing curves were measured to evaluate the corrosion resistance. The results show that the coatings are of porous structure and mainly composed of MgO. The thickness and surface roughness of three kinds of coatings abide by the following sequences: Mode 1 > Mode 2 > Mode 3. By comparison, “equivalent circuit” mode Rs{Q1[R1(Q2R2)]} is the most proper to reflect the structure of such coatings, including the surface roughness, the outer layer pore structure, and the inner layer structure. The coatings prepared under Mode 1 are of maximum thickness and high density, and therefore have the best general corrosion resistance. And the coatings prepared under Mode 3 are of the smallest surface roughness and higher density, which leads to the best pitting corrosion resistance.

Corrosion performance of AISI 316L friction surfaced coatings

Friction surfacing is a novel solid-state surfacing process with several advantages over conventional weld overlay processes. In this work, the corrosion behavior of AISI 316L stainless steel coatings made using friction surfacing and manual metal arc welding processes was comparatively evaluated. Friction surfaced coatings exhibited superior general and pitting corrosion resistance compared to manual metal arc coatings, while both the coatings were found to be immune to intergranular corrosion. Compared to alloy 316L bulk material, friction surfaced coatings showed better pitting corrosion resistance, but considerably lower general corrosion resistance.

Influence of the Current Density of Deposition on the Properties of Zn–Ni Coatings

Zn–Ni coatings were deposited under galvanostatic conditions at current densities varying within the range 20– 60 mA ⋅ cm –2 . The influence of the current density of deposition on the surface morphology, chemical and phase compositions, and corrosion resistance was investigated. Structural investigations were performed by the X-ray diffraction (XRD) method. The surface morphology and chemical composition of deposited coatings were studied by using a JEOL JSM-6480 scanning electron microscope. The studies of general electrochemical corrosion resistance were carried out in a 5% NaCl solution by using potentiodynamic and electrochemical impedance spectroscopy (EIS) methods. The local corrosion resistance was determined by the Scanning Kelvin Probe (SKP) method. On the basis of the research, the possibility of deposition of Zn–Ni coatings containing 14–18 at.% Ni was demonstrated. It was stated that the surface morphology, as well as the chemical and phase compositions of these coatings depend, to a small extent, on the current density of deposition. However, current density of deposition determines the quantity of zinc which is codeposited with nickel and is bounded in the form of an intermetallic compound or a solid solution. Small differences between the chemical composition and the uneven distribution of the Zn(Ni) and Ni2Zn11 phases on the surfaces of the coatings may cause differences in the local Kelvin potential. As a result, the Zn–Ni coatings exhibit corrosion resistances varying depending on the current density of deposition. The optimal values of the current density from the viewpoint of corrosion resistance were found to be j = 30– 40 mA ⋅ cm –2 .

Investigation on Chip Formation during Machining Using Finite Element Modeling

Titanium alloys are desirable materials for aerospace industry because of their excellent combination of high specific strength, lightweight, fracture resistant characteristics, and general corrosion resistance. Therefore, the chip morphology is very important in the study of machinability of metals as well as the study of cutting tool wear. The chips are generally classified into four groups: continuous chips, chips with built-up-edges (BUE), discontinuous chips and serrated chips. . The chip morphology and segmentation play a predominant role in determining machinability and tool wear during the machining process. The mechanics of segmented chip formation during orthogonal cutting of titanium alloy Ti–6Al–4V are studied in detail with the aid of high-speed imaging of the chip formation zone. The finite element model of chip formation of Ti–6Al–4V is suggested as a discontinuous type chip at lower cutting speeds developing into a continuous, but segmented, chip at higher cutting speeds. The prediction by using finite-element modeling method and simulation process in machining while create chips formation can contribute in reducing the cost of manufacturing in terms of prolongs the cutting tool life and machining time saving.

The Effect of Trace Boron on Corrosion Resistance of the Casted 0.04C-16Cr Ferritic Stainless Steels in H<sub>2</sub>SO<sub>4</sub> Medium

Three groups of 0.04C-16Cr ferritic stainless steels, with boron quality score of 0ppm, 16ppm and 26ppm, were smelted by a vacuum induction furnace. The chemical soak method, the tafel polarization curve method and the anode circular polarization curve method were used to research their general corrosion and intergranular corrosion resistance. The results showed that both general corrosion and intergranular corrosion of the casted 0.04C-16Cr ferritic stainless steels happened in dilute H2SO4 medium. The resuluts of electrochemical and chemical soak indicate that the addition of B improves intergranular corrosion resistance of 0.04C-16Cr stainless steel, moreover, the intergranular corrosion resistance increases with an increasing content of B. The addtion of B makes the general corrosion rate and self-corrosion current density of the 0.04 C-16Cr stainless steel reduced at active dissolution region in dilute sulphuric acid medium, so the general corrosion resistance of the 0.04 C-16Cr stainless steel is improved. The blunt-dimensional current density of the steel with 26ppm B is the lowest and the passivation zone of it is wider, so the stability of passive film and protection capacity of the steel with 26ppm B are the best. The electrochemical characteristics of general corrosion coincided with the results of soak corrosion.

Localized Corrosion of Thermally Aged Cast Duplex Stainless Steel for Primary Coolant Pipes of Nuclear Power Plant

Localized corrosion of cast duplex stainless steel Z3CN20.09M, which used widely in primary coolant pipes of nuclear power plants, has been investigated after thermally aged at 400°C for 100, 300, 1000 and 3000h by making use of electrochemical method. Double loop electrochemical potentiodynamic reactivation (DL-EPR) and potentiodynamic polarization tests were used for assessing intergranular corrosion (IGC), pitting and general corrosion resistance, respectively. The experimental results showed that the general corrosion resistance of Z3CN20.09M did not change almost with increase of thermal aging time, however, IGC and pitting corrosion resistance decreased. In the polarization curves, the peak anodic current density of general corrosion was not found to change almost with increase of thermal aging time, but DL-EPR results showed that the value of Ir/Ia increased. The deterioration in localized corrosion resistance of thermally aged specimen was directly related to the precipitation of alpha prime phase in ferrite by spinodal decomposition.

Sintered Materials for Bipolar Plates

Sintered Materials for Bipolar PlatesThis study presents an analysis of opportunities of the application of stainless steel for interconnectors in fuel cells. The investigations also included microstructural analysis of sintered materials in terms of use of them as interconnectors in proton exchange membrane fuel cells (PEMFC). Corrosion resistance in sinters made of a stainless steel was analysed in sulphate solutions; general corrosion resistance and pitting corrosion resistance were tested in the presence of chloride ions. Due to the multifunctionality of materials for interconnectors, selection of these materials is extremely difficult. Results of the investigations of corrosion resistance prove that corrosion resistance is connected with the structure of material and chemical composition of sinters.

Environmentally assisted cracking behaviour of plasma electrolytic oxidation coated AZ31 magnesium alloy

A wrought AZ31 magnesium alloy was plasma electrolytic oxidation (PEO) coated in phosphate and silicate based alkaline electrolytes. The effect of these PEO coatings on the stress corrosion cracking (SCC) behaviour of the alloy was investigated by slow strain rate tensile (SSRT) tests in ASTM D1384 solution. The untreated and PEO coated AZ31 magnesium alloy specimens were found to be susceptible to SCC, despite the fact that the PEO coatings offered an excellent general corrosion resistance. The results of the polarisation tests on the untreated AZ31 alloy specimen after prolonged immersion in ASTM D1384 electrolyte suggested the formation of a film on the surface constituted by the corrosion products. The cracking of this film and the evolution/ingress of hydrogen at these defective sites during the SSRT tests in the corrosive environment was believed to be responsible for the SCC of the untreated alloy. Similarly, the cracking of the PEO coatings during the SSRT test, the consequent exposure of the underneath magnesium alloy substrate and the associated electrochemical reactions were attributed as reasons for the SCC of the PEO coated specimens. The transgranular mode of fracture in all the cases avowed that the hydrogen induced cracking was the mechanism of SCC.

Investigation of corrosion behaviour of carbon steel coated by pulsed plasma electrolytic boronising technique in 3·5 wt-%NaCl aqueous solution

Boride coatings were synthesised on AISI H13 steel using pulsed plasma electrolytic boronising technique in a modified aqueous solution of borax. Hard and strongly adherent coatings with various desirable properties were obtained by applying different frequencies and duty cycles during the treatment. The analytical characteristics of the coating were assessed using X-ray diffraction and scanning electron microscopy techniques. The thickness of boride layers was increased by increasing frequencies. The corrosion performances of these coatings were investigated by a potentiodynamic polarisation test and ac impedance spectroscopy. Equivalent circuits have been proposed to represent the boride phases, oxide film and electrolyte systems examined. The general corrosion resistance of the produced coatings has been found to increase with the frequency.

Corrosion behavior of CuCrFeNiMn high entropy alloy system in 1 M sulfuric acid solution

AbstractImmersion tests and potentiodynamic polarization measurements were conducted in 1 M sulfuric acid solution (H2SO4) at ambient temperature (∼25 °C) to investigate the corrosion behavior of CuCrFeNiMn alloy system. The results show that the alloys display a good general corrosion resistance that is mainly influenced by the Cu content and elemental segregation degree. The corrosion resistance degrades when increasing Cu content and elemental segregation degree. Among the tested alloys, the CuCr2Fe2Ni2Mn2 alloy with low Cu content and elemental segregation degree displays a better general corrosion resistance. On the contrary, the Cu2CrFe2NiMn2 alloy with high Cu content and elemental segregation degree exhibits the worst general corrosion resistance.

The corrosion performance of die-cast magnesium alloy MRI230D in 3.5% NaCl solution saturated with Mg(OH) 2

The environmental behavior of die-cast magnesium alloy MRI230D designated for high-temperature applications was evaluated in comparison with regular AZ91D alloy. The microstructure examination was carried out using SEM, TEM, and X-ray diffraction analysis; the corrosion performance in 3.5% NaCl solution was evaluated by immersion test, salt spray testing, potentiodynamic polarization analysis, and stress corrosion behavior by Slow Strain Rate Testing (SSRT). Although the general corrosion resistance of MRI230D was slightly improved compared to that of AZ91D alloy its stress corrosion resistance was relatively reduced. The variations in the environmental behavior of the two alloys were mainly due to the differences in their chemical composition and microstructure after die casting. In particular, the differences were related to the reduced Al content in MRI230D and the addition of Ca to this alloy, which consequently affected its relative microstructure and electrochemical characteristics.

Electrochemical corrosion parameters of as-cast Al–Fe alloys in a NaCl solution

The aim of this study is to evaluate the general electrochemical corrosion resistance of Al–Fe alloys in the range of hypoeutectic compositions, Al–0.5 wt.% Fe and Al–1.5 wt.% Fe alloy. EIS plots, potentiodynamic polarization curves and an equivalent circuit analysis were used to evaluate the electrochemical parameters in a 0.5 M NaCl solution at 25 °C. It is shown that for an Al–0.5 wt.% Fe alloy, coarse cells tend to improve the corrosion resistance mainly due to the reduction in cellular boundaries and for an Al–1.5 wt.% Fe alloy, an opposite trend has been detected.

Microstructure features affecting mechanical properties and corrosion behavior of a hypoeutectic Al–Ni alloy

The aim of this article is to analyze the influence of microstructural parameters on the mechanical properties and corrosion behavior of a hypoeutectic Al–Ni alloy. Experimental results include secondary dendrite arm spacing, corrosion potential, current density, pitting potential, ultimate tensile strength and yield strength. It was found that cooling rates during solidification of about 0.6 °C/s and 8 °C/s can provide secondary dendritic spacings of 7 μm and 16 μm, respectively. Although the microstructure having their phases finely and homogeneously distributed was shown to induce better mechanical properties and higher pitting potential, its general corrosion resistance decreased when compared with the corresponding results of the coarser microstructure.

Effects of Carbon on the Corrosion Behaviour in Fe‐18Cr‐10Mn‐N‐C Stainless Steels

The effects of carbon on general and pitting corrosion behaviour of Fe-18Cr-10Mn-(0.33∼0.44)N-(0∼0.38)C alloys were investigated using potentiodynamic tests. Carbon made the nitrogen-bearing alloys inert and thus promoted general corrosion resistance. These results were supported by experimental findings, such as elevated corrosion potential, reduced active dissolution rate, lowered passive potential and accelerated hydrogen evolution rate in sulphuric acid solution. The resistance to pitting corrosion in chloride solution was also enhanced by the addition of carbon, which was attributed to the improvement of the stability of the passive film. XPS analysis revealed that the cationic fraction of chromium in the passive film was increased and hence the protection ability of the film was improved by the carbon addition.

Electrochemical corrosion characterization of Al–Ni alloys in a dilute sodium chloride solution

The aim of this study is to characterize the electrochemical corrosion resistance of Al–Ni alloy samples which were directionally solidified under upward unsteady state heat flow conditions. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques were used to analyze the corrosion resistance in a dilute 0.05 M NaCl solution at 25 °C. Equivalent circuit analyses were also conducted. It was found that microstructural features such as the dendritic arrangement and the distribution of Al 3Ni intermetallic particles have important roles on both the resulting pitting potential and the general corrosion resistance of Al–Ni alloys.

Multiaxial Forging of Super Duplex Steel

The investigated super duplex steel belongs to the group of stainless steels which exhibits an austenitic-ferritic microstructure with a phase fraction of about 50% austenite and 50% ferrite. The alloy shows excellent general corrosion resistance as well as a good resistance against stress corrosion cracking, corrosion fatigue and erosion corrosion. Due to these outstanding properties, the super duplex alloy is used in components for sea or waste water applications and in the offshore and chemical industry. In addition, the investigated super duplex steel exhibits a good weldability and a high strength in comparison to pure austenitic steel grades In order to optimize the production process and to provide a suitable microstructure to satisfy the customer’s requirements multiaxial forging test at various temperatures were performed in the Gleeble Maxstrain system. The force and the displacement after each anvil stroke were measured and used to distinguish the mechanical behaviour in the forging process at different thermal conditions. The recorded force and displacement is also compared with a multi step compression test to show the influence of change in the deformation direction. A certain number of samples were exposed an in-situ heat treatment after the deformation while other samples were immediately quenched after the forging to preserve the deformed microstructure, which was measured by optical microscopy and electron microscopy. Furthermore, electron back scatter diffractions scans were applied to characterize the degree of dynamic recrystallization during the forging process.

DMV 931

Abstract DMV 931 is an alloy for general and chloride corrosion resistance. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: SS-1047. Producer or source: Mannesmann DMV Stainless USA Inc.