Abstract
Inhibitors are regularly used as one of the principal prevention and control techniques in reinforcement corrosion. Hence this study investigates the effect of calcium nitrate and sodium nitrite inhibitors on the rebar corrosion of medium carbon steel in seawater and cassava fluid with a view to determining inhibitive potentials of the different inhibitors in the two media. Gravimetric and voltametric techniques were employed in this study and a total of forty-five corrosion coupons of different dimensions were produced. Forty coupons were used for gravimetric analysis and the remaining five for corrosion potentials measurements. Eight of the samples were used as control; while other eight samples each were admixed with calcium nitrate and sodium nitrite in concrete cubes. It was later immersed in seawater and cassava fluid for a total duration of 32 days and the measurements were taken at the interval of 4 days in order to determine the corrosion rates in mils per year (mmpy). Two controls and admixed samples each were later immersed in seawater and cassava fluid, respectively, for durations of 32 days to determine the corrosion potentials using a voltmeter and a Copper-Copper Sulphate Electrode (Cu/CuSO4). The pH of each medium was measured throughout the period of exposure. The results obtained expressed that all the samples except the control samples, displayed some degree of inhibition. The inhibition levels for the admixed samples in seawater were higher compared with those in cassava fluid. Inhibition efficiencies for various inhibitors followed different trends in different environment. The inhibition efficiencies for calcium nitrate in cassava fluid and seawater were 26.81% and 64.85% respectively. The study concluded that inorganic inhibitors were effective in inhibiting corrosion in cyanide and chloride contaminated concrete cubes.
Highlights
Corrosion is recognized as the number one life limiting plant degradation mechanism
The focus of this research is to investigate the inhibitive potential of calcium nitrate and sodium nitrite on the rebar corrosion of medium carbon steel in seawater and cassava fluid
It was observed from the graphs that samples immersed in cassava fluid exhibited severe corrosion rates compared with samples in seawater
Summary
Corrosion is recognized as the number one life limiting plant degradation mechanism It can attack insidiously yet the cumulative damage it inflicts and the cost of repair can be substantial and are well known but badly understood by those whose work involves the design, manufacture and maintenance of process equipment. This issue has resulted in the increasing interest in research into the environment/metal interface reactions and the means of reducing the damaging effects of corrosion on metals and alloys. The concomitant presence of sulphate salts with the chloride ions is known to aggravate the corrosive attack on reinforcing steel [4]. This study investigates the effect of calcium nitrate and sodium nitrite on corrosion associated with concrete industry
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