Corrosion resistance of AZ91 magnesium alloy with pulse electrodeposited Ni-SiC nanocomposite coating

Magnesium and its alloys are the lightest of the structural metals, which makes them one of the most promising materials to minimize vehicle weight, but poor surface properties restrict the application of these alloys. In this paper, Ni-SiC nanocomposite coatings were applied on AZ91 magnesium alloy from Watts bath with SiC content 0 g.L-1 (pure Ni), 10 g.L-1 (Ni-10SiC) and 15 g.L-1 (Ni-15SiC) by application of pulse electrodeposition technique. The morphology and phase analysis were carried out by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) analysis, respectively. Micro-hardness of specimens was measured and the results revealed a significant enhancement: from 74 Vickers for bare AZ91 magnesium alloy to 523 Vickers for coated specimen in the bath containing 15 g.L-1 SiC. The Corrosion behavior of the samples was studied by potentiodaynamic polarization, and the obtained data showed the superior corrosion resistance for the coated AZ91 magnesium alloy, i.e. the corrosion current density decreased from 2.69 mA.cm-2, for the uncoated sample, to 0.00046 mA.cm-2, for coated specimen in the bath containing 15 g.L-1 SiC and the corrosion potential increased from -2.069 V to -0.33 V for the same conditions

Improvement of adhesion, corrosion and wear resistance of Ni electrodeposited coating by applying Cu intermediate layer after zincate process

306-312Zincate treatment is extensively used for preparation of aluminium surface prior to deposition process. However, the zinc layer may be dissolved in acidic solutions such as Watts bath used for electrodeposition of Ni coating. Hence, the use of an intermediate layer between Zn film and top coating has been suggested. In this study, the effect of Cu intermediate layer on properties of Ni coating electrodeposited on 6061 Al alloys substrate is investigated. The properties of the coatings are studied by means of peel test, potentiodynamic polarization techniques and wear test. The results indicated that the use of Cu intermediate layer increased the adhesion strength of the coating from 0.85×103 N/m to 4.01×103 N/m. Furthermore, the corrosion and wear resistance of samples improved when Cu intermediate layer is applied after zincate process

Reliability assessment of wind load combinations based on Iranian National Building Code

The new generation of design codes is established by reliability-based calibration methods. The overall aims of these methods are to achieve consistent levels of safety or structural reliability under different type of uncertainties. According to these methods, the acceptable reliability level of structures is obtained based on statistical descriptions of loads and resistance and also consideration of different types of uncertainties such as the physical uncertainty, the statistical uncertainty and the model uncertainty. In the last decades, based on reliability-based calibration approaches, load and resistance factor design (LRFD) method has been developed for steel buildings design. In this method desired level of safety is obtained by a set of partial load and resistance factor. The design load combinations for steel structures in Iranian National Building Code (INBC), Part 6, are generally based on other codes such as ASCE/SEI 7-10 standard and National Building Code of Canada (for wind load factors), while the effect of Iranian statistical data for load and resistance has not been considered. In comparison to other loads, such as gravity loads, wind load has a high degree of uncertainty and also it is completely site dependent. Therefore it is important to estimate a suitable statistical model for wind load and also investigate the reliability level of structures subjected to wind load combinations. This paper is a parametric study to assessment the reliability level of wind load combinations for steel beams based on INBC. For this purpose, wind load statistical data are provided for whole of Iran by the climatology data of wind speeds. Based on the FOSM method explicit formulation for reliability index of beams is calculated. The reliability indices for a range of practical load ratios are obtained and compared to the target reliability index. The results indicated that reliability level of wind load combinations in INBC is lower than target reliability index. One of the main reasons for the low level of reliability index for wind load combinations is related to underestimation of reference speed. The results show that by considering the reference speeds based on statistical data, reliability index approaches to target reliability index