Experimental Investigation of the Corrosion Behavior of Friction Stir Welded AZ61A Magnesium Alloy Welds under Salt Spray Corrosion Test and Galvanic Corrosion Test Using Response Surface Methodology

Abstract

Extruded Mg alloy plates of 6 mm thick of AZ61A grade were butt welded using advanced welding process and friction stir welding (FSW) processes. The specimens were exposed to salt spray conditions and immersion conditions to characterize their corrosion rates on the effect of pH value, chloride ion concentration, and corrosion time. In addition, an attempt was made to develop an empirical relationship to predict the corrosion rate of FSW welds in salt spray corrosion test and galvanic corrosion test using design of experiments. The corrosion morphology and the pit morphology were analyzed by optical microscopy, and the corrosion products were examined using scanning electron microscope and X-ray diffraction analysis. From this research work, it is found that, in both corrosion tests, the corrosion rate decreases with the increase in pH value, the decrease in chloride ion concentration, and a higher corrosion time. The results show the usage of the magnesium alloy for best environments and suitable applications from the aforementioned conditions. Also, it is found that AZ61A magnesium alloy welds possess low-corrosion rate and higher-corrosion resistance in the galvanic corrosion test than in the salt spray corrosion test.

Welding of magnesium and its alloys: an overview of methods and process parameters and their effects on mechanical behaviour and structural integrity of the welds

“…Solid-state welding procedures involve joining of two metals without the application of heat [48,49]. However, heat is generated from the contact surfaces due to the movement of a fixed component part relative to a moving one.…”

“…There is also the need to fill very wide root gaps since it does not require the use of filler materials [153]. There is no melting involved in SSW and weld appearance are great with improved mechanical properties at the weld joint [49].…”

“…Friction stir welding is non-fusion solid state welding process. It uses a quasi-consuming, rotating tool with a pin, extending across the weld line from a wider shoulder to join metals together [49,156]. The weld is created by sequential spinning and forward movement of the instrument pin along the weld line, inducing friction and strong plastic deformation at temperatures below the melting point of the adjoining metals [156].…”

“…The weld is created by sequential spinning and forward movement of the instrument pin along the weld line, inducing friction and strong plastic deformation at temperatures below the melting point of the adjoining metals [156]. The process does not have welding defects such as shrinkage, hot fracturing and porosity, significantly reduces the thermal stresses induced in the metals [49,156]. A typical friction stir welding process is shown in Figure 6 [157].…”

Analysis of the inhibiting action of pectin on corrosion of AISI1040 dual-phase steel with ferrite–martensite and ferrite–bainite structure: a comparison in 0.5 M sulphuric acid

“…The optimization process is perhaps the most widely recognized application in corrosion chemistry to determine the levels of process parameters that result in a maximum value of an outcome [24][25][26][27][28][29]. Recently, multivariate techniques are frequently used in optimization studies because they require less time, reagents, and experimental work.…”