Corrosion Behavior Of Specimens Research Articles

Effects of Ambient Temperature and State of Galvanized Layer on Corrosion of Galvanized Steel in High-Humidity Neutral Atmosphere.

Galvanized steel is a cost-effective and corrosion-resistant material with high strength, making it a popular choice for various engineering applications. In order to investigate the effects of ambient temperature and galvanized layer state on the corrosion of galvanized steel in a high-humidity neutral atmosphere environment, we placed three types of specimens (Q235 steel, undamaged galvanized steel, damaged galvanized steel) in a neutral atmosphere environment with a humidity of 95% at three different temperatures (50 °C, 70 °C, and 90 °C) for testing. The corrosion behavior of specimens under simulated high-temperature and high-humidity conditions was studied using weight changes, macroscopic and microscopic observations, and analysis of the corrosion products of the specimens before and after corrosion. Emphasis was placed on examining the effects of temperature and damage to the galvanized layer on the corrosion rate of the specimens. The findings indicated that damaged galvanized steel retains good corrosion resistance at 50 °C. However, at 70 °C and 90 °C, the damage to the galvanized layer will accelerate the corrosion of the base metal.

Effects of mixed acid solution on bromide epoxy vinyl ester and its glass fiber reinforced composites

Abstract As fiber reinforced plastics (FRP) have been increasingly widely used, they may sometimes come into contact with several corrosive media simultaneously, for example, the condensate in the smokestack liners of coal-fired power FGD systems. To study the long-term performance and degradation mechanism of FRP in these complicated environments, an accelerated aging test of bromide epoxy vinyl ester (Br-VE) and its glass fiber reinforced composites (GF/VE) in a mixed acid solution(H2SO4, HNO3, HF and HCl) at three different temperatures(25, 55 and 80 °C) for 180 days was carried out. Weight changes, flexural properties, Fourier transforming infrared spectra (FTIR), dynamic thermal mechanical (DMA), macroscopic and microscopic morphology were investigated. Results showed that immersion temperature has important effects on the corrosion behavior of specimens. The long-term weight change behavior of GF/VE at normal temperature was in accordance with Fick’s second law, but deviated at higher temperature. Flexural properties of GF/VE declined more drastically than those of Br-VE at elevated temperatures. The Tg of GF/VE decreased with rising temperatures. Results also indicted that Br-VE and GF/VE manifested varied degradation mechanisms when subject to the same mixed acid medium immersion. The degradation of GF/VE mainly involved plasticization, embrittlement, the hydrolysis of resin, an ion exchange between HF, H+ and Si-O-Si or alkali metal of the fiber as well as the debonding of the resin/fiber interface.

Fatigue and Corrosion Behavior of Solid-State Recycled Aluminum Alloy EN AW 6082

In this research, a solid-state recycling process of aluminum was performed. It consisted of aluminum EN AW 6082 alloy machining chip cold precompaction and hot extrusion followed by a combination of equal channel angular pressing (ECAP) and heat treatment. The main aim of this paper is to determine the fatigue and corrosion behavior of the recycled specimens. In order to determine the recycled specimen fracture mode after fatigue testing, fractography analysis was performed. The corrosion behavior of all specimens was investigated in 0.5 M NaCl solution using open circuit potential measurements, polarization and electrochemical impedance spectroscopy (EIS) methods. It was found that the corrosion resistance of the tested specimens is similar for reference and as-extruded recycled specimens, while it is increased for those which were additionally processed with equal channel angular pressing and heat treatment. Namely, the corrosion current decreased in the same order, while the polarization resistance increased. Impedance measurements have shown that the subsequent plastic deformation and heat treatment of recycled specimens facilitated passivation of tested materials and improved surface film properties, which is confirmed with scanning electron microscopy and energy-dispersive x-ray spectroscopy. Fatigue life was similar for recycled and reference specimens for the selected stress levels. However, fractography showed that multiple cracks appeared inside the recycled specimens which caused different crack propagation mechanisms compared with reference specimens.

Effect of Silane-Treated Mineral Fillers on Corrosion, Wettability, and Adhesion of Saturated Polyester Coated on Carbon Steel

Saturated polyester (PE) resin was modified with 0.5 and 1.0% (v/v) of epoxysilane-treated (aluminosilicate, muscovite, nepheline syenite, and wollastonite) and alkoxysilane-treated (aluminosilicate) mineral fillers before coating to carbon steel. The corrosion behavior of specimens was studied using potentiodynamic polarization method. Wetting behavior and adhesion of specimens were evaluated by static contact angle and cross-cut tape tests, respectively. The addition of silane-treated mineral fillers dramatically improved the corrosion resistance of saturated PE, with epoxysilane-treated wollastonite and alkoxysilane-treated aluminosilicate at 0.5% concentration significantly lowering the corrosion tendency and rate in 2 M HCl solution. Meanwhile, only epoxysilane-treated nepheline syenite significantly increased the water contact angle of saturated PE. The adhesion of saturated PE to carbons steel was increased after addition of fillers at 0.5%, with epoxysilane-treated wollastonite and alkoxysilane-treated aluminosilicate giving the lowest percent area removed after application of adhesive tape. Epoxysilane-treated wollastonite and alkoxysilane-treated aluminosilicate at 0.5% were found most suitable as fillers for saturated PE coating.

Plasma Electrolytic Oxidation (PEO) Process on Commercially Pure Ti Surface: Effects of Electrolyte on the Microstructure and Corrosion Behavior of Coatings

The current study investigates the ceramic oxide coatings formed on commercially pure Ti substrate via plasma electrolytic oxidation (PEO) technique in electrolytes with different chemical compositions. The effects of electrolyte on the discharge characteristics, macro- and micro-structure, thickness, phase compositions, and corrosion behaviors of coatings were evaluated. Five kinds of electrolytes based on the sodium salt compounds including aluminate, phosphate, silicate, aluminate-phosphate, and aluminate-silicate were used. The PEO processes were carried out at fixed voltage (420 V) for 180 seconds. The morphology and phase composition of samples were investigated using scanning electron microscope (SEM) and X-ray diffractometer (XRD), respectively. The corrosion behavior of specimens was analyzed in a 3.5 wt pct NaCl solution using the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests. The results showed that the most uniform and dense structure with less porosity was obtained in the coating prepared in aluminate-phosphate-based electrolyte. This coating consisted of TiO2 (Rutile and Anatase) and TiAl2O5 phases. Also, it was confirmed that the noblest corrosion potential and lowest corrosion current density, and consequently, the best corrosion behavior (22.96 × 107 Ω cm2), were observed for aluminate-phosphate-based electrolyte. The Mott–Schottky analysis exhibited that all samples had n-type semiconducting behavior. The coating prepared in aluminate-phosphate-based electrolyte possessed the lowest donor densities.

In-vitro bioactivity and electrochemical behavior of polyaniline encapsulated titania nanotube arrays for biomedical applications

Titania nanotube arrays (TNTA) have attracted increasing attention due to their outstanding properties and potential applications in biomedical field. Fabrication of titania nanotubes on titanium surface enhances the biocompatibility. Polyaniline (PANI) is one of the best conducting polymers with remarkable corrosion resistance and reasonable biocompatibility. In this work, the corrosion resistance and biocompatibility of polyaniline encapsulated TiO2 nanotubes for orthopaedic applications were investigated. The vertically oriented, highly ordered TiO2 nanotubes were fabricated on titanium by electrochemical anodization process using fluoride containing electrolytes. The anodization parameters viz., voltage, pH, time and electrolyte concentration were optimized to get orderly arranged TNTA. Further, the conducting polymer PANI was encapsulated on TNTA by electropolymerization process to enhance the corrosion resistance. The nanostructure of the fabricated TNTA and polyaniline encapsulated titania nanotube arrays (PANI-TNTA) were investigated by HR SEM analysis. The formed phases and functional groups were find using XRD, ATR-FTIR. The hydrophilic surface of TNTA and PANI-TNTA was identified by water contact angle studies. The corrosion behavior of specimens was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization studies. In-vitro immersion studies were carried out in simulated body fluid solution (Hanks’ solution) to evaluate the bioactivity of the TNTA and PANI-TNTA. The surface morphological studies revealed the formation of PANI on the TNTA surface. Formation of hydroxyapatite (HAp) on the surfaces of TNTA and PANI-TNTA enhanced the bioactivity and corrosion resistance.

Characterisation of localised corrosion behaviour of Ti-Ta-Mo alloy for the nuclear industry

AbstractIn this study, Ti-Ta-Mo alloy specimens were produced by powder metallurgy for the nuclear industry. For evaluating application of Ti alloys as components for nuclear fuel reprocessing plants, corrosion behaviour of Ti-Ta-Mo alloy was investigated. Localised corrosion (crevice and pitting) behaviour of the Ti-Ta-Mo alloys containing 5–15 wt.% Mo was investigated in 10 wt.% NaCl solution. The effect of composition of the alloys on the corrosion behaviour of specimens was studied. Resistance against localised attack was found to depend on the Mo content of the alloys. Mechanical properties (Young’s modulus) of the specimens were investigated by nondestructive ultrasonic tests.

Corrosion mechanism of 13Cr stainless steel in completion fluid of high temperature and high concentration bromine salt

Abstract A series of corrosion tests of 13Cr stainless steel were conducted in a simulated completion fluid environment of high temperature and high concentration bromine salt. Corrosion behavior of specimens and the component of corrosion products were investigated by means of scanning electron microscope (SEM), confocal laser scanning microscopy (CLSM) and X-ray photoelectron spectroscopy (XPS). The results indicate that 13Cr steel suffers from severe local corrosion and there is always a passive halo around every pit. The formation mechanism of the passive halo is established. OH − ligand generates and adsorbs in a certain scale because of abundant OH − on the surface around the pits. Passive film forms around each pit, which leads to the occurrence of passivation in a certain region. Finally, the dissimilarities in properties and morphologies of regions, namely the pit and its corresponding passive halo, can result in different corrosion sensitivities and may promote the formation of macroscopic galvanic pairs

Chemical corrosion by chlorides on ancient-like bronzes and treatment by hydrogen glow discharge plasma

Three representative ancient-like bronzes are employed for the chemical synthesis of Cu2(OH)3Cl rich patinas in order to study the influence of the alloying elements in the evolution of the chloride attack and to further conduct stabilization treatment via Hydrogen Glow Discharge Plasma (HGDP) at low temperature and pressure. The corrosion behavior of specimens having Sn and Pb as main alloying elements is governed by a decuprification mechanism and by the formation of Sn–Pb–O enriched barrier layers. In the case of the Zn containing alloy, dezincification is more pronounced at the corrosion initial stages, and copper species predominate the corrosion products evolution. A three-hour HGDP treatment leads to Cu+ production and metallic Cu, Sn, Zn, and Pb redeposition, as a result of metal cation reduction. This process is accompanied by partial removal of Cl species, O diminution, and change in coloration. The further increase of the Cl/O atomic ratio measured on the post-treated surfaces leads to the formation of nantokite and thus to the conclusion that the stabilization of objects with extensive Cl attack is not feasible by HGDP without preliminary chemical treatment.

Corrosion Behavior of some Sintered CuNi Alloys – Preliminary Laboratory Data

The paper aims to discuss some aspects on corrosion behavior of specimens from sintered CuNi alloys (e.g. Cu90Ni10; Cu70Ni30). The above mentioned specimens were manufactured by dissimilar laboratory routes: from alloyed powders, from elementary powders and from mixtures consisting of Cu80Ni20 alloy and an alloying element. Research aims to establish the manufacturing parameters influence on sintered specimens characteristics (density, porosity, microstructure features) in order to correlate them with corrosion tests laboratory data. There were investigated the corrosion mechanisms in relation with macro- and microstructure properties of the sintered specimen surface. For comparison purposes, it is intended to extend the analysis to Cu60Ni40 and Cu80Ni20 sintered alloys.

Effect of iron content and annealing temperature on the corrosion behavior of Ni100−xFex

Ni100−xFex metallic glasses have been prepared with 8.5 ≤ x ≤ 51 using electrodeposition technique. Corrosion behavior of specimens in 0.1 M Na2SO4 (pH = 6) at 25°C has been studied using potential-time decay, linear polarization resistance and potentiodynamic techniques. Anodic polarization curves show that the specimens exhibit quasi-passive region. The dissolution of samples increases with the increase of iron concentration and also with the increase of annealing temperature. The interpretation was based on the enhanced dissolution of the formed microcrystals of the specimens in the sulphate solution.