Papers by Keyword: Corrosion Morphology

Abstract: A challenge in producing a sacrificial anode through conventional casting method is that the alloying elements in casting segregate during solidification, which further causes non-uniform anode corrosion reducing anode performance. In this paper, we investigated the performance of Al-5Zn-0.02In anode produced by conventional casting compared with by semi-solid casting technique. The performance of produced anodes were measured in terms of anode potential, current capacity, consumption rate and anode efficiency in 3.5% NaCl solution for 14 days. We found that the microstructure of the conventional cast anode had dendrites and coarse grains and the corrosion caused pitting corrosion. In contrast, the semi-solid cast anode had fine grains without any dendrites. The corrosion attacked mainly the grain boundaries and less on the matrix. Surprisingly, the conventional cast anode has about 10% higher efficiency than that of semi-solid cast anode.

Abstract: Abstract: Oxidized and non-oxidized SiC particulates were mixed with Al powder respectively and the two kinds of mixed powders were consolidated at 250°C by equal channel angular pressing and torsion (ECAP-T), which belongs to severe plastic deformation. The interfacial bondings of as-consolidated composites were characterized by SEM images, corrosion morphology and fracture morphology. The results show that after severe plastic deformation, the interfacial bonding between non-oxidized SiC and Al is a kind of mechanical bonding and the consolidation is not firm enough so that the composite has a weak corrosion resistance and its tensile sample has a brittle fracture. However, the composite containing oxidized SiC has a dense microstructure, high corrosion resistance, ductile fracture due to the metallurgical interface.

Abstract: In this paper the effect of solution treatment on the corrosion resistance of welding joint of Ni56Cr22Mo13 alloy was studied by polarization curves, mass loss method, SEM. The results indicated that the composition of alloy welded was not uniform and the corrosion resistance of welding joint of Ni56Cr22Mo13 alloy was poor. After solution treatment, the corrosion resistance was enhanced.

Abstract: New waterborne Al-Zn-Si-RE coatings with improved corrosion resistance were introduced in this study. The corrosion resistance of Al-Zn-Si-RE coatings was evaluated by electrochemical measurements and salt spray test. Evolution of microstructure and phase composition at different exposure time in salt spray test was investigated by scanning electron microscopy and X-ray diffraction technique. The results indicate that Al-Zn-Si-RE coatings provide effective sacrificial protection to the steel substrate but exhibit lower corrosion rate and higher corrosion resistance compared to zinc aluminum coatings. The dense continuous corrosion layer formed on Al-Zn-Si-RE coating acts as a barrier layer, limiting the transport of aggressive species towards the coating-substrate interface and the corrosion rate of the coating; Zinc aluminum hydroxy carbonates are the dominant components in the corrosion layer of Al-Zn-Si-RE coatings.

Abstract: The corrosion behavior of rebar HRB400 in 0.5 wt.%, 1.5 wt.% and 3.5 wt.% NaCl solutions was investigated by corrosion rate calculation and corrosion morphology observation. The results showed that, with the increase of corrosion time from 240h to 720h, the corrosion rate of rebar HRB400 in each NaCl solution increases. With the increase of NaCl solution concentration, the corrosion rate of rebar HRB400 increases. The corrosion morphologies show strong consistency with the test results of corrosion rate.

Abstract: The corrosion behavior of reinforcing bar HRB335 in 3.5 wt.% NaCl solution was investigated, and the tensile mechanical properties after corrosion were tested. The results showed that, with the increase of corrosion time, the corrosion rate of reinforcing bar HRB335 increases and the corrosion becomes heavier. Meanwhile, the yield strength and tensile strength decrease, but the elongation decreases at first and then increases.

Abstract: The corrosion behaviors of Al-Zn-Sn and Al-Zn-Sn-Ga alloys were investigated according to the results of immersion tests and corrosion morphology observation，and the Fermi energy of the precipitates was calculated by Materials Studio software for discussing the corrosion kinetics of precipitates . The results show that the Al-Zn phase with high Fermi energy (low corrosion potential) dissolved firstly, than caused the forming of Al-Ga amalgam which deposited between passive film and Al matrix. Meanwhile, the Al-Ga phase with higher Fermi energy dissolved too, which made the Al-Zn-Sn-Ga alloy continue to active, Finally, the Al-Zn-Sn-Ga alloy formed uniform corrosion morphology due to the effect of Al-Ga amalgam, while Al-Zn-Sn alloy formed the surface feature with the deep corrosion pits due to the "self-catalysis" mechanism.

Abstract: The corrosion behavior of 304L and 316L stainless steel have been investigated in 55 °C,85% food grade phosphoric acid solution by weight loss method and dynamic potential scan , the surface morphology was observed by scanning electron microscopy(SEM). The results showed that the number of pits in 304L was much more than that in 316L. The contents of Cr inside pits were greater than that in the smooth surface in the two stainless steels, indicating the Cr-poor are prone to corrosion. All the samples exhibited stable passive behavior which can be seen from the potentiodynamic polarization curves, 316L corrosion potential (-0.201V) was higher than that of 304L the corrosion potential (-0.357V), and under the same circumstance, 316L stainless steel was more corrosion-resistant than 304L stainless steel.

Abstract: The relation between corrosion depth and width with corrosion time is according with the power function. The corrosion pits can be seen as ellipse balls through the examination of QUESTAR three-dimensional optics microscope. Corrosion can decrease the fatigue life of materials and is the main reason of fatigue crack form and grow; through AFGROW analyze we can see that the AFGROW software can simulate crack growth life well and the error is low, the crack growth life and critical crack length are conservative than experiment values.

Abstract: The pre-corrosion damage tests of LC4 aluminum alloy with the shot peening surface treatment and un-shot peening surface treatment are performed under two different time levels: 12h and 24h. Based on the observation of the corrosion morphology of aluminum alloy, the corrosion damage mechanism of shot peening aluminum alloy can be divided into three stages: intergranular corrosion occurs first, and then denudation generates, at last pitting corrosion occurs as denudation depth reaches a certain degree. For shot peening aluminum alloy, the denudation depth, mass loss and the total depth of corrosion damage are used to represent the corrosion characteristics. With the corrosion time increase, the three parameters all increase correspondingly.