Water yam (Dioscorea alata) flour was processed using standard wet milling procedure prior to the extrusion process, which led to the determination of extrudate properties of the flours. A single‐screw extruder (DCE 330, NJ) was used in evaluating the extrudate properties, which included torque, mass flow rate, residence time, specific mechanical energy and expansion ratio of the flours from the water yam samples. The effect of extrusion and process variables: feed moisture content, screw speed and barrel temperature on the extruder torque, residence time, mass flow rate, specific mechanical energy and expansion ratio for the variety were determined and predictive models were also developed using response surface methodology. It was observed that changing the feed moisture content, barrel temperature and screw speed significantly (P < 0.05) affected expansion ratio, torque, mass flow rate, residence time and specific mechanical energy of all the extrudates. Increasing the feed moisture content (18–28% db) and screw speed (80–180 rpm) resulted in a substantial decrease in expansion ratio (46.6%), residence time (27.5%) and specific mechanical energy (83.6%); whereas, increasing the screw speed significantly increased the mass flow rate (64.5%) of extrudates. Regression analysis indicated that screw speed and feed moisture content were the major process variables showing significant (P < 0.05) linear, quadratic and interaction influences on mass flow rate, expansion ratio and specific mechanical energy. PRACTICAL APPLICATIONS This investigation was conducted with a broad intention of enhancing the value of water yam flours and its suitability for incorporation in the production of noodle‐like products. This was accomplished by varying the feed moisture content, screw speed and barrel temperature, and determining their effects on resulting extrudate properties.

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The consequences of corrosion are many and varied, and their effects of these on the safe, reliable and efficient operation of equipment or structures are often more serious than a simple loss of metal mass. This research investigates the corrosion performance of two nonferrous metals in three acidic media, namely sulfuric acid (98% volume of H 2 SO 4 ), hydrochloric acid (75% volume of HCl), and trioxonitrate (V) acid (75% volume of HNO 3 ). The corrosion rate is determined by the weight loss method, and the characterization of metallic samples is obtained by scanning electron microscope (SEM). The SEM shows the cracking pattern of grains indicating surface erosion due to the corrosion effects which are more depicted on the zinc than aluminum samples. It is shown that the solution of H 2 SO 4 has the highest impact on the corrosion rates of metallic samples, whereas the least effect is observed on the solution of HNO 3 . It is observed that Zn alloy sample in 3 M H 2 SO 4 records the highest corrosion rate of 138.64 mm/year, while the aluminum alloy sample has the lowest rate of 24.661 mm/year after 72 hours of exposures in the acid. The corrosion rates of the samples decrease as the exposure time increases. The weight loss intensity increases with exposure time for Al samples and varies for Zn sample in acidic media. In conclusion, the higher the acid molarity, the shorter the exposure time and the higher the corrosion rates for both zinc and aluminum alloy samples. K E Y W O R D Sacidic media, aluminum and zinc alloys, characterization, corrosion rate, weight loss method 1This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

This study was carried out to investigate the effect of heat treatment (Normalizing and Hardening) on the mechanical properties of springs. The springs were made from mild steel rod having a diameter of 6 mm, a total of 15 springs were made. The springs were then subjected to various heat treatment processes which included; normalizing, hardening and tempering. The heat treated springs were then subjected to various test in other to determine their mechanical properties, these included; impact toughness test, hardness test and tension test. The normalized spring had more strength, was harder and was much tougher than both the annealed and as received springs. The water quenched springs were the hardest of all the heat treated springs, were very brittle and had the lowest percentage elongation. Their strength was also lower than that of the normalized and as received springs. The water quenched and tempered springs had better mechanical properties required for spring making, they had the optimum combination of hardness, strength and toughness when compared with the other heat treated springs.

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