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The corrosion behaviors of Fe83‐XC1B11Si2P3CrX (X = 0, 1, 2, and 3 at%) amorphous alloys in 0.1 M NaCl solution have been investigated by immersion and electrochemical tests. With the addition of Cr content from 0 to 3 at%, the corrosion rate of amorphous alloys gradually decreases from 2.57 × 10−1 to 1.04 × 10−1 mm·year−1. The minor addition of Cr improves the corrosion resistance through the increase in the Ecorr value, which makes it easy to reach a passive state and suppress pitting corrosion. The corroded morphology and products of amorphous alloys have been tested by scanning electron microscopy (SEM) and energy‐dispersive spectroscopy (EDS). The SEM/EDS analysis shows that the high corrosion resistance is due to the formation of dense and stable chromium oxide during immersion in NaCl solutions. [ABSTRACT FROM AUTHOR]

The corrosion performances of Mg–4Y–xAl (x = 1, 2, 3, and 4 wt%) alloys in the 3.5% NaCl electrolyte solution are investigated by electrochemical tests, weight loss measurement and corrosion morphology observation. The results indicate that corrosion modes for the alloys are localized corrosion and the filiform type of attack. With Al concentration increasing from 1 to 4 wt%, the corrosion rate of Mg–4Y–xAl alloys decreases firstly and then increases, and WA42 alloy shows the best corrosion resistance. The addition of Al element to Mg–4Y alloys leads to the formation of Al2Y and Al11Y3 intermetallic compounds and reduces the proportion of Mg24Y5 phase. Corrosion resistance of the Mg–4Y–xAl alloys mainly depends on the size and distribution of the second phases. Besides, the addition of excessive Al can greatly consumes the Y element in the matrix, thus leading to a less protective film on the alloys. The effect of the relative Volta potential changes between the second phases and α‐Mg on corrosion resistance of Mg–4Y–xAl alloys is insignificant. The main corrosion products of the Mg–4Y–xAl alloys are Mg(OH)2, Mg3(OH)5Cl·4H2O, Mg0.72Al0.28(CO3)0.15(OH)1.98(H2O)0.48, and Mg4Al2(OH)12CO3·3H2O. [ABSTRACT FROM AUTHOR]

Mechanical property and corrosion behavior of 7A46 aluminum alloy under peak-ageing (T6), double-ageing (DA) and pre-ageing (PA) followed by double-ageing (PA-DA) are systematically investigated. The hardness and strength of aged 7A46 alloy follows an order of T6>PA-DA > DA and the rank of corrosion resistance is PA-DA > DA > T6. The small size and dispersed distribution of matrix precipitates (MPs) lead to the high hardness and strength of T6 alloy, and low hetero-phase potential differences and less formation probability of corrosion galvanic couples enhance the corrosion resistance of PA-DA alloy. Intergranular corrosion (IGC) test results reveal that considerable potential differences promote the formation rate and the quantity of corrosive-batteries between the matrix and grain boundary precipitations (GBPs) or precipitate-free zones (PFZs). The exfoliation corrosion (EXCO) rate and the weight gain trend of corrosion products are related to the oxide film formation rate and corrosion products accumulation. Localized anodic dissolution and hydrogen embrittlement can induce the stress cracking corrosion (SCC). • The strengthen mechanism of 7A46 alloy is studied. • The mechanical strength is related to the small dispersed particles. • The alloy exhibits the best corrosion resistance under PA-DA condition. • The corrosion rate of the alloy under PA-DA condition is lower than that under T6, DA condition. [ABSTRACT FROM AUTHOR]

The influence of the addition of nano-scaled bioactive glass (nBG) powder into polycaprolactone (PCL) coatings on the biodegradation and bioactivity of pure Mg was investigated in the present work. Scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), Fourier transform infrared spectroscopy (FTIR) and electrochemical methods were employed to characterize the morphology, chemical composition and anticorrosion properties of the coatings. The results indicate that nBG addition in PCL increases the degradation of PCL in physiological solution; depending on the amount of nBG in the composite coating, the barrier properties of PCL therefore can be modified. At the same time, the addition of nBG facilitates the formation of hydroxyapatite during 7 days immersion in simulated body fluid (SBF). [ABSTRACT FROM AUTHOR]

Abstract: Silica coatings have been applied on the surface of ZE41 magnesium alloy following the organic sol–gel route and the dip-coating technique. Three different concentrations of sol solution and two densification temperatures of the coating (400°C and 500°C) were used to optimize the compaction of the coatings and as a result reach the corrosion protection of the metallic substrate tests in 3.5wt.% NaCl aqueous solution. Crack-free coatings with thickness in the 2–3μm were obtained on the ZE41 magnesium alloy. The combination of high alkoxide concentration in the sol–gel formulation, and the high sintering temperature (500°C) leads to coating (D500) with the optimal physical barrier against the corrosion process. This coating was capable of resisting more than 7days in contact with the aggressive electrolyte suffering minor corrosion degradation. A corrosion mechanism for each of the tested specimens has been proposed. [ABSTRACT FROM AUTHOR]

The short service life of bearings in galvanising industry is a result of a complex set of deterioration mechanisms. This work addressed the effect of temperature and molten bath reactivity on the material of the bearings respectively. Three commercial alloys, the Co-Cr-W Stellite 6 and Co-Cr-Mo-Si Tribaloy (T400 and T800) alloy systems, were deposited by plasma transferred arc on AISI 316L plates. Coatings were evaluated for the effect of temperature exposure on hardness, microstructure and sliding abrasive wear. The reactivity with the molten 55Al-Zn alloy was assessed by immersion tests in an industrial bath. Results showed that exposure at 600°C for 168 h resulted in an increase in hardness, microstructure changes and loss of wear resistance for the Stellite 6 coatings. A superior performance to temperature was shown by Tribaloy T800 with a stable abrasive wear resistance. The three alloys exhibited a strong reactivity with the 55Al-Zn molten bath. An intermetallic layer formed on the coatings as the Al from the bath reacted with elements from the Co based alloys. This reactivity consumed the coatings, causing a reduction on thickness particularly on those processed with the T800 alloy. [ABSTRACT FROM AUTHOR]

Rare earth (RE) elements are beneficial to improving corrosion properties in low-carbon and low-alloy steels. In this paper, corrosion performance of Q235B steel and Q355B steel samples after RE alloying under wet-dry cycle immersion conditions were analyzed. Experimental results show that corrosion rate was significantly decreased. It was probably due to the grain refinement by RE alloying, which increased the density of protective rust layers and improved corrosion resistance. The formation of small-sized spherical RE inclusions also inhibited the precipitation of MnS and weakened micro galvanic corrosion. Additionally, RE atoms tended to segregate towards grain boundaries and a RE concentration region is formed between rust layers and matrix to impede the access from contacting corrosive ions. A corrosion resistance schematic of RE atom segregation was proposed based on microstructure morphology and element distribution results. [ABSTRACT FROM AUTHOR]