No abstract

Enormous funds are spent on the protection of engineering components and structures annually as a result of corrosion. Degradation sets in, due to electrochemical reaction that takes place between materials and the environment leading to reduced performance. The associated downtime caused by replacement and maintenance of vessels, pipes, valves and other equipment necessitated seeking for techniques and method to efficiently combat corrosion. This study evaluated the potentiodynamic polarization of brass, Coated Mild Steel (CMS) and Stainless Steel (SS) in sodium chloride (NaCl). The samples (1 x 30 x 30 mm3) were used as working electrodes for Potentiodynamic Polarization Experiment (PPE). The samples were cleaned, and soaked in 1M NaCl solution. Open circuit potentials and current densities of the samples were obtained from PPE which were used to evaluate their corrosion rates. The pH of the media was recorded before and after each experiment. The results obtained using PPE in NaCl (in mm/y) were 0.209, 0.0053 and 0.0046; for brass, MSC and SS respectively. The pH of the medium was measured as 10.9.The results revealed that brass had highest corrosion rate in the medium. The least corrosion rate was obtained for Stainless Steel in 1M NaCl followed by Coated Mild Steel.

This work researched into the use of metakaolin as a partial substitute for cement in concrete, metakaolin was obtained by the calcination of kaolin clay to about 700 0 C Cement was replaced with the metakaolin at 0,5,10,15,20, 25, 30, and 35% at water cement ratio of 0.5. Tests such as chemical analysis, compressive strength, flexural or modulus of rupture and bond strength were carried out on the concrete samples. Chemical analysis results showed that the metakaolin is a class "N" pozzolan, while the mechanical test showed that the strength of concrete increased from 5% to 20% replacement, and the strength peaked at 20%, but decreased above this value; concrete made with metakaolin performed better than the control sample at all the percentage replacements used in this work.

The moisture diffusivity and activation energy of three tilapia fish varieties were determined under convective drying process (CDP). A locally fabricated drying system was used for the experiment at 60, 90/60 and 90 o C drying air temperatures. The drying rate showed falling rate period for all the drying processes with no sign of constant rate period. The moisture diffusivity values which increased with the increase in drying air temperature varied from 7.821 x 10-11 to 4.591 x 10-10 m 2 /s. The predicted Arrhenius constant and activation energy were 2.221 x 10-10 m 2 /s and 23.79 kJ/mol respectively.