Alloys In Different Environments Research Articles

Recent Progress on Atmospheric Corrosion of Field-Exposed Magnesium Alloys

It is well known that the poor corrosion resistance of magnesium alloys is a key factor limiting their application. Field exposure is the most reliable means to evaluate the atmospheric corrosion performance of magnesium alloys. This article reviews the field exposure corrosion behavior of magnesium alloys in typical atmospheric environments (including the marine atmosphere, industrial atmosphere, etc.) in recent years. According to the literature review, it was found that there are significant regional differences in the atmospheric corrosion behavior of magnesium alloys, which is the result of the coupling of multiple factors in the atmospheric environment. By investigating the corrosion rate and corrosion products of different types of magnesium alloys in different environments, the corrosion mechanism of magnesium alloys in different environments was summarized. Specifically, environmental parameters such as atmospheric temperature, relative humidity, CO2, and chloride ion deposition rates in the marine atmospheric environment can affect the corrosion behavior of magnesium alloys. The corrosion of magnesium alloys in different industrial atmospheric environments is mainly affected by atmospheric temperature and relative humidity, as well as atmospheric pollutants (such as SO2, CO2, NO2) and dust. This review provides assistance to the development of new corrosion-resistant magnesium alloys.

Stress corrosion cracking susceptibility of a new nickel‐based alloy in different environments

AbstractStress corrosion cracking (SCC) susceptibility of a new nickel‐based alloy C‐HRA‐2 under two types of superheated steam (SHS) (0.1 and 8 MPa) and supercritical water (SCW) (25 MPa) at 650°C was studied through slow strain rate tensile tests at a strain rate of 5 × 10−7 s−1. The results indicate that C‐HRA‐2 exhibits SCC susceptibility in both SHS and SCW, and the susceptibility increases with increasing pressure. Transgranular fracture (located inside) characterized by dimples/micropores and intergranular fracture (located at the edge) characterized by rock‐sugar‐like morphology was observed in all specimens. The brittleness of the alloy increases with the increase of medium pressure. A large number of cracks perpendicular to the loading axis were noticed on the gauge surface. The SCC mechanism of C‐HRA‐2 under steam and SCW is dynamic embrittlement.

Understanding stress corrosion cracking behavior of 7085-T7651 aluminum alloy in polluted atmosphere

The electrochemical and Stress Corrosion Cracking (SCC) behaviors of 7085-T7651 aluminum alloy in different environments are studied by electrochemical and mechanical testing. The research shows that the type, concentration of the corrosive medium and electrolyte state affect the electrochemical and SCC controlling processes of aluminum alloys. The Thin Electrolyte Layer (TEL) state and the addition of HSO3– increase the corrosion rate and SCC susceptibility. The presence of HSO3– in a corrosive environment can significantly accelerate the corrosion rate and mechanical property degradation, and this effect increases with the increase of HSO3– concentration. Compared with the solution environment, the TEL environment will further aggravate corrosion and mechanical property degradation. With the increase of HSO3– concentration, the pH of the corrosive environment exhibits little change, while the SCC degradation is significantly promoted. This is attributed to the HSO3– induced buffer effect and film-assisted stress effect, yielding the overshadowing effect against solution pH.

Trihexyltetradecylphosphonium bis(Trifluoromethylsulfonyl) imide as inhibitor for 6063 aluminium alloy corrosion in physiological solution

Aluminium alloys have found extensive use in several industrial, biological and dentistry applications, due to their high resistance towards corrosion in certain environments compared with carbon steels. Moreover, this choice is also related to the relatively low cost of the aluminium alloys. The use of aluminium alloys in the biological and dentistry related applications is of special importance. The addition of inhibitors presents an effective method for the reduction of the corrosion of the aluminium alloys in different environments. In this paper, the corrosion of 6063 aluminium alloy in physiological solution, with and without the addition of trihexyltetradecylphosphoniumbis(trifluoromethylsulfonyl) imide has been discussed. The influence of the inhibitor’s concentration on the corrosion rate of the 6063 aluminium alloy in physiological solution at 37°C, was studied using the weight loss and the potentiodynamic polarization techniques. The increase in the concentration of the trihexyltetradecylphosphoniumbis(trifluoromethylsulfonyl) imide added resulted in increased resistance of the 6063 aluminium alloy in the studied corrosion environment.

The COVID-19 Pandemic, Part 1: Can Antimicrobial Copper-Based Alloys Help Suppress Infectious Transmission of Viruses Originating from Human Contact with High-Touch Surfaces?

The COVID-19 Pandemic, Part 1: Can Antimicrobial Copper-Based Alloys Help Suppress Infectious Transmission of Viruses Originating from Human Contact with High-Touch Surfaces?

Fracture Surface of a Ti-6Al-4V Specimen with EDM Notches Tested under Quasi-Static Loading in Methanol

Ti-6Al-4V titanium alloy is a high strength-to-mass ratio material common in a lot of engineering fields. Its surface oxide can guarantee the protection of the substrate from various corrosive media. Unluckily, this film can be scratched in presence of mechanical and chemical loads and for this reason the corrosion resistance can decrease. The Structural Mechanics Laboratory (SM-Lab) is carrying out a characterization of the alloy in different environments under quasi-static loading. In this paper, a summary of the outcomes of the investigation and the description of the fracture surface of a specimen with EDM notches quasi-statically tested in methanol is provided

Effects of niobium particles on the wear behavior of powder metallurgical γ-TiAl alloy in different environments

The wear behavior of a powder metallurgical γ-TiAl alloy, Ti-45Al-5Nb-0.4W + 2Nb (in at. %), containing Nb particles was investigated using pin-on-disk wear tests at room temperature. The dry sliding wear tests were performed against a zirconia disk in different environments: argon, a hydrogen in nitrogen mixture, air and oxygen. The wear rates of the TiAl pins were significantly greater in the presence of oxygen but little affected by water vapor or molecular hydrogen. The worn surface of the TiAl pins and the wear debris were examined using both a scanning electron microscope and an X-ray diffractometer. The tribolayer in the Nb rich area near the worn tip of the pin was investigated using transmission electron microscopy on specimens prepared by focused ion beam milling. It was found that both pure Nb particle residues present in the β phase of the alloy and new compounds precipitated in the Nb-rich area around the Nb particles substantially enhanced the wear-resistance. The zirconia disk underwent a phase transformation induced by the high stresses and temperature during the wear tests. The abrasive particles produced during the wear testing, which largely consisted of the zirconia particles, were found to be embedded into a tribolayer on the worn tips of the TiAl pins. The results indicate that the main wear mechanisms of the (Ti-45Al-5Nb-0.4W) + 2Nb alloy were two-body and three-body abrasive wear, some delamination, and plastic deformation.

Stress Corrosion Behavior of AM50Gd Magnesium Alloy in Different Environments

A new type of high strength corrosion-resistant magnesium alloy was prepared by adding 1% rare earth Gd to AM50 and then treated with hot extrusion method. The stress corrosion properties of the new materials in air, pure water, 0.5 mol/L NaCl, and 0.5 mol/L Na2SO4 solution were studied by the slow strain rate tensile (SSRT) test, in situ open circuit potential test, Tafel curve test, stereomicroscope, SEM, and EDS. The results showed the following. The stress corrosion sensitivity of the material in different environments was Na2SO4 > NaCl > distilled water > air. According to the Tafel curves measured at 0 and 100 MPa, the corrosion voltage decreased little and the corrosion current density increased rapidly under 100 Pa. This was because the film of the corrosion product ruptured to form a large cathode and a small anode, which resulted in a large instantaneous corrosion current. The mechanism of hydrogen embrittlement and anodic dissolution together affected the stress corrosion behavior of the alloy. In distilled water, hydrogen embrittlement played a major role, while in NaCl and Na2SO4 solution, hydrogen embrittlement and anodic dissolution were both affected. The direct reason of the stress corrosion crack (SCC) samples’ failure was the cracks expanding rapidly at the bottom of pit, which was caused by corrosion.

Wear Behavior of P/M High Nb Containing γ-TiAl Alloy in Different Environments

The wear behavior of Ti–45Al–7Nb–0.3W (at%) alloy prepared by powder metallurgy (P/M) has been investigated using pin-on-disk wear tests at the room temperature. The dry sliding wear tests were performed against on a zirconia disk in different environments, viz, argon, hydrogen in nitrogen mixture, air and oxygen. The worn surfaces of Ti–45Al–7Nb–0.3W pins and wear debris were examined by scanning electron microscope, X-ray diffractometer and X-ray photoelectron spectroscopy. It was found that the high Nb containing Ti–45Al–7Nb–0.3W alloy didn’t exhibit better wear resistance in the presence of oxygen than commercial γ-TiAl (Ti–47Al–2Nb–2Cr–0.2W) alloy. The oxidation on the worn surface and spalling of oxides caused by the mechanical force during sliding were the main reason for the high wear losses in the air and oxygen. The zirconia disk underwent a phase transformation caused by the high contact temperature and stress during the sliding tests. The abrasive particles produced in the wear tests largely consisted of the zirconia particles in different environments, except in the pure oxygen. The hard zirconia debris was embedded into the friction layer on the worn surfaces of TiAl pins, which provided protection against wear to some extent. The main wear mechanisms of Ti–45Al–7Nb–0.3W alloy were abrasive wear of two-body and three-body, some delamination and plastic deformation.

The Relationship of High Strength Aluminum Alloy Corrosion Behavior and Corrosion Environment

The aim of this article is to research the characteristics of corrosion pit on 2xxx aluminum alloys in different environments (3.5wt% NaCl solution, water in fuel tank and wet air). Measure the area of corrosion pit, the depth of corrosion pit in different environments. The results show that in 3.5wt% NaCl solution: the initiation of surface corrosion pits mainly occur in 24h, with time increasing ,the depth of corrosion pit rises indistinctively; in water in fuel tank : during 24h-120h, with the extension of corrosion time, the maximum depth of corrosion pits changed a little, the maximum corrosion area became a little smaller than that in 3.5wt% NaCl solution; in wet air: the corrosion damage was smaller than that in 3.5wt% NaCl solution and water in fuel tank, the depth of the corrosion pit was about 20μm, the biggest size of corrosion pit area was about 0.5 x104μm2.

High-frequency corrosion fatigue behavior of AZ31 magnesium alloy in different environments

The high-frequency corrosion fatigue behavior of extruded AZ31 magnesium alloy was investigated in different environments: air, gear oil and 3.5% NaCl solution. Compared with that in air, the corrosion fatigue limits were degraded by approximately 3.52% and 58.91%, respectively, and the corrosion fatigue lives were shortened by about 13.43% and 89.36%, respectively. In the same environment, the high-frequency fatigue limits are all higher than those tested at low frequency. The specimen geometrical shape plays a certain factor on stage characteristics of S–N curves. Compared with that of arc transition specimens, the stress sensitivity of line transition specimens is only reflected in a relatively high cycle fatigue life region. Different environments influence the corrosion failure kinetics processes (the crack initiation mechanism), but do not change the fatigue fracture mechanism of the alloy, and the higher loading frequency only accelerate the crack nucleation processes.

Corrosion studies of modified organosilane coated magnesium–yttrium alloy in different environments

Magnesium (Mg) and its alloys have numerous potential applications as biodegradable implants, but the fast degradation rate of Mg alloys at the initial implanted stage could be a problem. This paper describes the modification of the water-based bis-[triethoxysilyl] ethane (BTSE) silane applied to the surface of magnesium–yttrium (Mg–4Y) to increase its corrosion resistance. Surface characterization by SEM, FTIR, and EDX showed that the hydrolysis and condensation of the silane resulted in a covalent bonding to the Mg–4Y surface. Corrosion behavior of the uncoated and coated Mg–4Y alloy was evaluated in different environments by using a novel self-developed corrosion probe. Based on the electrochemical results of DC polarization and electrochemical impedance spectroscopy (EIS), we conclude that the epoxy-modified BTSE silane coating successfully increases the corrosion resistance at the initial stage of implantation. The corrosion rates in the flesh of dead mice environments such as body cavity and subcutaneous tissue of the mice were lower than the corrosion rates in in vitro environments.

Fatigue crack propagation and fracture mechanisms of wrought magnesium alloys in different environments

Fatigue crack propagation (FCP) was studied on wrought magnesium alloys, AZ31 and AZ61, in laboratory air, dry air and distilled water. In laboratory air, the FCP rate versus stress intensity factor plots consisted of two sections with different slopes, which was clearly recognized after allowing for crack closure. This was attributed to the transition in fracture mechanisms operated. In distilled water, FCP rates were nearly the same as in laboratory air, while in dry air, an order of magnitude slower than in laboratory air and distilled water. After allowing for crack closure, the environmental effects still existed and FCP rates were the fastest in laboratory air, then in distilled water, in dry air in decreasing order. Fractography revealed that the fracture mechanisms operated in laboratory air and in distilled water were different, possibly hydrogen embrittlement and anodic dissolution, respectively.

Electrochemical behavior of multicomponent amorphous and nanocrystalline Zr-based alloys in different environments

Electrochemical behavior of multicomponent melt spun Zr-based amorphous as well as nanocrystalline alloys have been studied in three different corrosive media (neutral NaCl, basic NaOH and acidic H 2SO 4 solutions). Due to the presence of strong passivating elements, (Zr and Ti) melt spun ternary alloys (Zr 55Ti 25Ni 20) have shown complete passivation in NaCl solution even as they contain a small amount of crystallinity. Amorphous multicomponent alloys containing Cu (Zr 58Cu 28Al 10Ti 4 and Zr 65Cu 7.5Al 7.5Ni 10Pd 10) show active nature in NaCl solution and this is strongly related to selective dissolution of base metal (Zr) and enrichment of Cu in the pit region. In NaOH and H 2SO 4 solutions, all the alloys have shown complete passivation irrespective of the alloy composition.

Electrochemical behaviour of amorphous and nanoquasicrystalline Zr–Pd and Zr–Pt alloys in different environments

The corrosion behaviour of melt spun amorphous and nanoquasicrystalline Zr 70Pd 30 and Zr 80Pt 20 alloy ribbons has been investigated using potentiodynamic polarization study in NaCl, H 2SO 4 and NaOH solutions at different concentrations. The amorphous and nanoquasicrystalline alloys show better corrosion resistance than Zr in all the solutions studied. Both the alloys are susceptible to chloride attack and pitting has been observed. Complete passivation has been observed in H 2SO 4, while gradual break down of passivating layer occurs in NaOH. In general, nanoquasicrystalline state in both the alloys shows better corrosion resistance than amorphous state in all the solutions studied.

Corrosion Resistance of Cupronickels - An Overview

Cupronickel alloys have been extensively used in marine and offshore applications. These alloys offer desirable physical and mechanical properties to be used as a versatile engineering alloy. The oxidation resistance of these alloys was due to the formation of scales consisting of a thick, inner Cu2O layer and a thin, outer CuO layer, together with nickel rich internal oxide. These alloys are superior to bronzes in their corrosion resistance but fail under oxidizing conditions. In sulphide atmospheres they undergo sulphidization. Depending upon the alloy composition, they form layers consisting of alloy/nickel sulphide/CuS of various proportions. In chloride solutions, they undergo localized attack. For lower chloride concentration, an increase in nickel content worsens the resistance to passive film breakdown, where as for higher chloride concentration an increase in the nickel content favour passivation. In seawater, the prime source is dissolved oxygen and the corrosion product is Cu2O. This is formed by the hydrolysis of CuCl2-. The use of ozone enhanced the dissolved oxygen content. Localised attack occurred at those points where the seawater is in motion. The impingement and general corrosion resistance was improved by the addition of iron in the alloy. Sulphides and ammonia as pollutants adversely influenced the performance of the alloy. Microbial adhesion alters the protective properties of the complex layers of the alloy. The bacteria enhanced the corrosion rates in seawater with intergranular corrosion and denickelification. The minor additions of an element, use of inhibitors in the medium and cathodic protection are the main methods of corrosion control in aqueous media. The various aspects of the corrosion resistance behavior of cupronickel alloys in different environments are discussed in the review

Corrosion behaviour of silver brazing alloys in different environments

Corrosion data of the widely used silver brazing alloys (BAg‐1 and BAg‐3) of the American Welding Society’s (AWS) specification are scant in literature. Deals with the study of the corrosion behaviour of these alloys in different environments with particular emphasis on the industrial and marine atmospheres.

The use of stainless steels and related alloys in reverse osmosis desalination plants

Metallic components are essential to the successful operation of reverse osmosis plants. Corrosion conditions in these plants are often severe and it is important to select the correct material to optimise cost and performance. The authors discuss the corrosion properties of stainless steels and related alloys in different environments and give guidelines on the selection of materials for the components of reverse osmosis systems.