The aim of this work is to study the effect of austenizing time, tempering process and tempering time on corrosion rate of austenitic stainless steel in oxalic acid. The samples of typical 304 stainless steel were heated to 1050°C for 10, 20 and 30 minutes and quenched to room temperature in water, then tempered at 250°C, 400°C and 600°C for 30, 60 minutes for each tempering time. These samples were then immersed in 0.1M of oxalic acid and then their weight losses were measured after 30 days. The result obtained show that corrosion rate of all austenitic stainless steel samples decreased with an increase austenizing time, this behaviour is due to more homogenously of austenite, and the corrosion rate will be increased with increase the tempering temperature and tempering time, this behaviour is due different phases at microstructure below 400°C, and above of 400 to 600°C the corrosion rate will be increased due to formation of carbides which are non-uniform distributed at the grain boundaries and causes intergranular corrosion.
Abstract. The metals anodization process used to enhance the surface hardness and corrosion resistance. This study developed a durable hard Nano copper oxide coating on copper using anodization technique in solutions of 0.1 to 0.5 M oxalate concentrations and 0 to 24 ο C operating temperature. The settings of the process parameters determined by using Taguchi's experimental design method. The EDX and XRD results confirm the formation of cupric oxide coating with monoclinic lattice crystalline structures. The FESEM results for the coated samples showed that the grain size was in the range between 25 to 68 nm. Microhardness tests for the anodized copper samples characterized by microhardness tester. Analysis of Variance for the orthogonal arrays of Taguchi identified that the most affecting parameter on the microhardness of the coating was the anodizing temperature. The results show that the hardness of the anodized coating was decreased with the anodizing temperature, where maximum hardness, with smaller grain size, were produced at lower anodizing temperatures.
Abstract. In this paper, Response surface methodology (RSM) was utilized to design the experiments at the settings of CuSO 4 and H 2 SO 4 concentrations and current densities. It also used for modelling and optimize the parameters on the adhesion strength of austenitic stainless steel substrate. The adhesion strength was investigated by the Teer ST-30 tester, and the structure of the samples investigated by using scanning electron microscopy (SEM). The modelling approach adopted in the present investigation can be used to predict the adhesion strength of the copper coatings on stainless steel substrate of electroplating parameters in ranges of CuSO 4 100 to 200 g/ L, H 2 SO 4 100 to 200 g / L and current density 40 to 80 mA / cm 2 . The results showed that, operating condition should be controlled at 200 g/L CuSO4, 100 g/L H2SO4 and 80 mA/cm 2 , to obtain the maximum adhesion strength 10N. IntroductionCopper is one of the metals most extensively used in industry, either because of its intrinsic properties or as a base for further formation of metallic films. Electroplating is one of the methods most generally used to obtain metallic films of equal thickness, porosity-free construction and good adhesion [1][2]. Electroplating copper films have been widely investigated with regard to their structural characteristics, electrical properties and corrosion resistance [3-4] but less care has been yielded to their mechanical behaviour and its relation to Electroplating parameters. By controlling variables such as current density and bath concentration, a variety of pictures with different characteristics can be attained, therefore allowing to tailor the mechanical characteristics of the coatings for specific applications. One of the most important mechanical properties of the coatings is the adhesion strength, which is defined by The ASTM as the "condition in which two surfaces are held together by either valence forces or by mechanical anchoring or by both together" [1]. (Teer ST-30) Scratch test is one of widely used, fast, and effective methods to obtain the critical loads that are related to adhesion properties of the coating [5][6]. A survey in 2001 showed that the scratch test is the most common test method used for measuring the quality of the coatings in industries [7]. In most experimental studies of concentration process, conventional methods were used to determine the influence of operational parameters. When using the conventional methods to optimize the process, one parameter is changed while others are kept at a constant level. This should be repeated for all influencing parameters, resulting in a great number of experiments [8]. Its major disadvantage is that it does not include the interactive effects among the variables studied. To overcome this problem, using a second-order model is useful in approximating a portion of the true response surface with parabolic curvature. The second-order model includes all the terms in the first-order model, plus all quadratic terms and all cross-product terms. It is us...
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