Faculty of Engineering

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Subject: search.filters.subject.Aluminium

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    Inhibition efficiency of gold nanoparticles on corrosion of mild steel, stainless steel and aluminium in 1M HCl solution
    (Elsevier, 2021-01-01) Jamiu Kolawole Odusote; Adeolu Adesoji Adediran; R.A. Yahya; Adekunle Akanni Adeleke; J.G. Oseni; J.M. Abdul; Tesleem B. Asafa; S.A. Adedayo
    In this study, the influence of gold nanoparticles (AuNPs) on corrosion behavior of mild steel, aluminium and stainless steel in 1.0 M HCl was investigated. The nanoparticles were previously characterized using FTIR, UV–Vis and TEM. Five concentrations of AuNPs solution (0 µg/ml, 5 µg/ml, 10 µg/ml, 15 µg/ml, 20 µg/ml) were added to 1M HCl. The corrosion rates of the metal samples and inhibition efficiency of the nanoparticles were analyzed using gravimetric (weight loss) and potentiodynamic polarization techniques. After 2000 h of exposure, gravimetric study showed that weight loss was reduced by ∼75% translating to ∼85% reduction in corrosion rate for the solution containing 20 µg/ml of AuNPs. The equivalent inhibition efficiency was 88%, 98% and 96% for aluminium, mild steel and stainless steel, respectively. Furthermore, potentiodynamic polarization results showed that the presence of AuNPs modified the mechanism of anodic dissolution by the formation of adsorption layer on the surface of the metal samples. These results indicated that AuNPs can be incorporated into existing inhibitors towards minimizing corrosion rate.
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    Corrosion rates of green novel hybrid conversion coating on aluminium 6061
    (Elsevier, 2020-08-19) Makanjuola Oki; A.A. Adediran; Peter Pelumi Ikubanni; O.S. Adesina; Adekunle Akanni Adeleke; S.A. Akintola; F. Edoziuno; A. Aleem
    The use of chromate conversion coatings have been limited by several protocols as a result of their carcinogenicity and toxicity towards humans and the environment. Searches are ongoing for chromate replacement in coating baths and processes. This paper describes the comparison among the corrosion rates of a novel hybrid conversion coating derived from water extracts of hibiscus sabdariffa calyx in conjunction with ammonium molybdate, a molybdate conversion coating and the so-called chromate conversion coating. Potentiodynamic polarization measurement in 3.5 ​wt% sodium chloride solution was employed in ranking the coatings as sabdariffa molybdate being more corrosion resistant than chromate, which in turn out performed molybdate.
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    Scanning and transmission electron microscopy examinations of composite hybrid chromate and chromate phosphate conversion coatings exposed in hot 100% relative humidity environments
    (Elsevier, 2023-07-20) Peter Pelumi Ikubanni; Makanjuola Oki; Adesoji A. Adediran; Sarah A. Akintola; Adekunle Akanni Adeleke
    Conversion coatings are sine qua non in the finishing of aluminium alloys. They may be put into service without coating of paints. However, for aesthetics in architectural applications, paint overcoat is common. Chromate phosphate coatings are relatively less toxic than chromate which gained the pride of place until recently. Thus, aluminium specimens coated with hybrid chromate/phosphate conversion coatings have been subjected to 100% relative humidity for 480 h at 313K in comparison to chromate coatings and bare aluminium. Scanning electron microscopy examination revealed that initial dried river bed morphologies on coated specimens were obliterated. The friable outer coatings collapsed into the cracks/environment leaving a relatively smooth surface after exposure. Additionally, transmission electron microscopy of sections before and after exposure revealed similar texture and morphological striations nearly parallel to each other throughout the length of the coatings to the metal/coating interface. These were not disrupted as well as the metal/coating interface which remained relatively smooth with no visible corrosion products after exposure. Thus, the coatings formed effective barrier between the substrate and the relatively harsh environment. From EDS, elemental compositions were the same albeit, spectral intensities remained relatively constant after humidity exposure regimes. The coatings are made up of either Cr, O and Al for chromate and Cr, P, O and Al for chromate/phosphate. At deliberately breached regions, the coatings prevented spread of corrosion and paint delamination over the substrates. On the other hand, bare aluminium was decorated with mounds of hydrated aluminium oxide/hydroxide after exposure as revealed in the SEM/TEM.