IOSR Journal of Applied Chemistry (IOSR-JAC) e-ISSN: 2278-5736.Volume 12, Issue 8 Ser. I (August. 2019), PP 44-50 www.iosrjournals.org DOI: 10.9790/5736-1208014450 www.iosrjournals.org 44 |Page Mechanism of Corrosion Inhibition of Aluminium in Potassium Hydroxide Using 2.0 M Thiourea. Okeke P. I., Enemo E. R., Ezenwa T. E. Department of Pure and Industrial Chemistry, Chukwuemeka Odumegwu Ojukwu University Uli, Anambra State, Nigeria. Corresponding author: Okeke P. I Abstract: The mechanism of corrosion inhibition of aluminium by 2 M thiourea in 0.08 M potassium hydroxide was investigated using gasometric, gravimetric and scanning electron microscope (SEM) methods. Synergistic measurements were also carried out, The result showed that the rate of hydrogen gas evolution and weight loss was greatly reduced while inhibition efficiency increased. These effects were seen to increase as time prolonged. SEM results showed the vivid presence of the absorbed inhibitor molecules on the surface of the metal protecting it from corrosion attack. Keywords: Corrosion inhibition, Aluminium, KOH, Gasometric, Gravimetric, SEM. --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 06-08-2019 Date of acceptance: 22-08-2019 --------------------------------------------------------------------------------------------------------------------------------------- I. Introduction Corrosion occurs as a result of the deterioration of metals and its related alloys due to electrochemical reaction with its immediate environment [1-2]. Aluminium is of notable economic, industrial and environmental importance. It is also a useful material for engineering applications due to its low cost, high electrical and thermal conductivity. Its light weight makes it of great choice in aircraft production. Aluminium and its alloys are commonly put to use in many industrial settings such as pharmaceutical industries, food industries, chemical batteries, pipes and reaction vessels. The corrosion of aluminium in alkaline environment can be controlled or reduced by the addition of inhibitors [3-5]. Protection of metals from corrosion using inhibitors has been applied to many systems such as in refinery units, oil and gas production units, boilers, aircraft units, etc. The choice of an appropriate inhibitor for a type of system is actually complicated. This is as a result of their specificity and so many varieties of corrosion-related applications. The highly corrosive nature of an alkaline medium on aluminium requires a good degree of protection to achieve economic maintenance, maximum safety, minimal loss of materials, quality and continuous operation of equipments. The development of corrosion inhibitors of non-toxic type, with absence of heavy metals and inorganic phosphates is now of a high importance [6-9], inorganic compounds such as nitrates and chromates have been largely used as corrosion inhibitors for different metals in several media, however, the toxicity and non environmentally friendly nature of these inorganic compounds especially chromates have been well reported which limits their applications [10-13]. Effective inhibitors are expected to perform optimally under wide range of conditions, this necessitates special care and attention in the selection of inhibitors for applications of various kinds. II. Experimental section 2.1 Materials preparation The aluminium alloy AA1060 used for this experiment is 0.045cm in thickness and composition in weight % as follows: Si (0.35), Fe (0.7), Cu (0.15), Mn (0.05) and Al (balance). The specimen was mechanically pressed cut into 2 x 2 cm coupons. The two faces had a total geometric surface area of 8.0 cm 2 . The coupon were degreased in absolute ethanol, dried in warm air, and stored in moisture free desiccators before labouratory analysis. 2.2 Gasometric measurements Gasometric assembly is an apparatus that measures the volume of gas evolved from a chemical reaction. A reaction system is connected to the burette through a delivery tube. 200 mL of the corrodent was introduced into the flask and the initial volume of the air in the burette was recorded. Then, aluminium coupon was introduced into the corrodent and the flask immediately closed. The volume of the hydrogen gas evolved from the corrosion reaction was monitored by the volume change in the level of paraffin oil in the burette. The change in volume was recorded every 5 minutes for 2 hrs and the results were tabulated.