Leading Corrosion Research in Africa
BioNano and Corrosion Science at Covenant
- Adsorptive desulphurization of model oil by Ag nanoparticles-modified activated carbon prepared from brewer's spent grains
- Polycyclic aromatic hydrocarbons in imported Sardinops sagax: Levels and health risk assessments through dietary exposure in Nigeria.
- C10H18N2Na2O10inhibition and adsorption mechanism on concrete steel-reinforcement corrosion in corrosive environments
- Effects of Phyllanthus muellerianus leaf-extract on steel-reinforcement corrosion in 3.5% NaCl-immersed concrete
- Adsorption and corrosion inhibition properties of thiocarbanilide on the electrochemical behavior of high carbon steel in dilute acid solutions
- Electrochemical analysis of the corrosion inhibition properties of 4-hydroxy-3-methoxybenzaldehyde on low carbon steel in dilute acid media.
- Electroless Nickel Plating – A Review
- Effects of Phyllanthus muellerianus leaf-extract on steel-reinforcement corrosion in 3.5% NaCl-immersed concrete.
- Diameter inconsistency, strength and corrosion characteristics of locally-produced and imported steel reinforcing bars in Ilorin, Nigeria
- Surface characterization, mechanical properties and corrosion behavior of ternary based Zn-ZnO-SiO2composite coating of mild steel
- Multifaceted incorporation of Zn-Al2O3/Cr2O3/SiO2nanocomposite coatings: anti-corrosion, tribological, and thermal stability.
- Sequence diversity among bad and virus isolates infecting yam (Dioscorea spp.)
- Survey of the incidence and distribution of five viruses infecting yam in the major yam-producing zones
- Competition between biofuel feedstock and food production
- Aflatoxins Microbial degradations.
- Contamination of fermented foods in Nigeria with fungi.
ABSTRACT: This study reports removal of dibenzothiophene (DBT) from model oil (DBT dissolved in n-heptane) by silver nanoparticles modified activated carbon prepared from brewer's spent grains using wet impregnation (WI) method. The removal efficiency follows the order AgNPscw/AC > AgNPskp/AC> ACB. The AgNPskp/AC and AgNPscw/AC exhibit higher adsorption capacities for DBT with maximum values of 25.7 and 29.8 mg DBT/gAds at 25 °C respectively, than ACB with 13.9 mg DBT/gAds. The two-fold enhancement in the DBT uptake capacities of modified ACs can be attributed to the introduction of Ag(1) ion, a weak Lewis acid as an additional adsorption site. A significant decrease from 212.9 to 136.2 m2/g in the Brunauer-Emmett-Teller surface area of AgNPscw/AC is observed following the loading of DBT. The equilibrium adsorption data is adequately represented by Freundlich isotherm. The adsorption kinetics of DBT by these adsorbents followed pseudo-second-order (PSO) model and the mechanism of adsorption was controlled by film and intra-particle diffusion. The change in entropy and heat of adsorption for DBT adsorption by these adsorbents range from 0.18 to 0.19 kJ/mol K and 21.5 to 23.9 kJ/mol, respectively. The results indicate that Ag nanoparticles-modified ACs from brewer's spent grains can be used as an adsorbent for the removal of DBT from model oil.
ABSTRACT: Polycyclic aromatic hydrocarbons (PAHs) occurrence and assessment of dietary exposure from imported canned sardines (Sardinops sagax) commercially marketed in local stores and supermarkets in Nigeria were evaluated for the first time. PAHs determinations were performed using high-performance liquid chromatography (HPLC) (Agilent 1290 model) equipped with UV-VIS diodes array detector (DAD) at λ = 210 nm and 214 nm. The percentage recoveries were higher than 96%. The degree of contamination expressed as the total concentration of PAH congeners ranged between 2.53 and 35.55 μg kg−1 dry weight (d.w.) at λ = 210 nm, and 1.30 and 27.93 μg kg−1 (d.w.) at λ = 214 nm. The carcinogenic (TEQBaP) and mutagenic toxicities (MEQBaP) of eight priority PAHs were evaluated. Benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene and indeno[1,2,3-c,d] pyrene contributed significantly to the total carcinogenic equivalents of PAHs. The mutagenic equivalents were largely dominated by chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene and benzo[a]pyrene and indeno[1,2,3-c,d]pyrene equivalence factors. The estimated lifetime average daily dose (LADD), average annual excess risk (AR), excess cancer rate (ECR), and hazard quotient risk (HQ) were evaluated for adults, children and preteens exposure-related risks. The LADD, ECR, AR, and HQ of PAHs for carcinogenic and non-carcinogenic risks are relatively higher in preteens than children and adults.
ABSTRACT: C10H18N2Na2O10 (ethylenediaminetetraacetic acid disodium salt) inhibition and adsorption mechanism on the corrosion of steel-reinforcement corrosion in concrete immersed in corrosive environments were investigated in this paper. For this, seven different concentrations ranging from 0% to 0.667% C10H18N2Na2O10 per weight of cement were admixed in steel-reinforced concretes immersed in saline and in acidic sulfate test-media and these were monitored using electrochemical techniques. Statistical analyses of the scatter of measured data from these, as per ASTM G16-95 R04, showed that C10H18N2Na2O10> 0% admixtures portrayed excellent efficiency at inhibiting steel-reinforcement corrosion in the saline environment. However, attaining comparably high inhibition of steel-reinforcement corrosion in concrete immersed in the acidic sulfate environment exhibited a greater dependency on high C10H18N2Na2O10 admixture concentration in the steel-reinforced concretes. Different models of adsorption isotherms bear indications of chemical adsorption, chemisorptions, as the prevalent adsorption mechanism of C10H18N2Na2O10 on steel-reinforcement in both of the corrosive environments.
ABSTRACT: This paper investigates Phyllanthus muellerianus leaf-extract effects on steel-reinforcement corrosion in concrete immersed in 3.5% NaCl, simulating the saline/marine environment. Different concentrations of the leaf-extract were admixed in steel-reinforced concrete samples, which were immersed, with normal control, in the test-environment, while positive control samples were immersed in distilled water. Electrochemical measurements of corrosion-rate (by linear-polarization resistance instrument), corrosion-current (by zero-resistance-ammeter) and corrosion-potential (by high impedance multimeter) were obtained for assessing the reinforcing steel corrosion. Analyzed results showed that the corrosion-rate exhibited excellent correlation (R = 98.82%, Nash-Sutcliffe Efficiency = 97.66%, ANOVA p-value = 0.0006) with function of the admixture concentration and of the corrosion noise-resistance (ratio of corrosion-potential and corrosion-current standard deviations). The 0.3333% Phyllanthus muellerianus (per weight of cement) exhibited optimal efficiency, η = 97.58% ± 1.28% (experimental) or 95.33% ± 4.25% (predicted), at inhibiting concrete steel-reinforcement corrosion in the test-environment, which compares well with the positive control performance model, η = 97.96% ± 0.03%. The experimental and predicted models followed the Langmuir adsorption isotherm, which indicated physisorption as the Phyllanthus muellerianus leaf-extract adsorption mechanism on the reinforcing steel. This support suitability of the N-, S-, and O-containing and π-electron rich Phyllanthus muellerianus leaf-extract as an environmentally-friendly inhibitor for effective corrosion-protection of steel reinforcement in concrete designed for the saline/marine environment.
ABSTRACT: The inhibition performance of thiocarbanilide on the electrochemical corrosion behavior of high carbon steel in 1 M H2SO4 and HCl acid solutions was studied through weight loss method and potentiodynamic polarization test. Data obtained showed that the organic compound performed effectively in acid solutions at all concentrations with an average thiocarbanilide inhibition efficiency above 70% in H2SO4 acid and 80% in HCl acid from weight loss and potentiodynamic polarization test respectively. Results from corrosion thermodynamic calculations showed that the adsorption of thiocarbanilide onto the steel was through chemisorption mechanism whereby the redox electrochemical process responsible for corrosion and the electrolytic transport of corrosive anions were simultaneously suppressed. Statistical derivations through ANOVA analysis confirm that the influences of both the inhibitor concentration and exposure time on inhibition efficiency values are negligible. Adsorption of the compound was determined to obey the Langmuir and Frumkin isotherm model.
ABSTRACT: The electrochemical behavior of low carbon steel in 1 M H2SO4 and HCl acid was studied in the presence of 4-hydroxy-3-methoxybenzaldehyde (HMD) as the inhibiting organic compound through weight loss and potentiodynamic polarization technique. Results show HMD has strong corrosion inhibition effects on the steel in the acid solution. HMD performed excellently at all concentrations studied with optimal inhibition efficiency of 96.6 and 92.5% from weight loss analysis and 88.81 and 91.35% for potentiodynamic polarization tests in H2SO4 and HCl. The compound showed mixed inhibition properties in both solutions. Data from statistical analysis through ANOVA shows the overwhelming influence of inhibitor concentration in H2SO4 and exposure time in HCl on the inhibition efficiency of the organic compound. Adsorption of the compound obeyed the Langmuir isotherm. Thermodynamic calculations showed strong physiochemical interactions and spontaneous adsorption mechanism.
Electroless Nickel Plating – A Review
ABSTRACT: The operating process, versatility and the increasing research interest in optimizing the process and products technology in the electroless plating method of metal coating, particularly, the electroless nickel plating of metallic substrates such as mild steel, necessitates the writing of this review. It is also aimed at providing more literature information, both of the past and the present published research in this field. In this paper, electroless nickel plating is introduced. The various nickel plating solutions and baths’ operating parameters; main types of electroless nickel plating; the mechanism involved in the plating process; application of the nickel plating process to iron powders; advantages and disadvantages and the process’s other applications are reviewed. Electroless nickel plating produces an amorphous deposit in the as-plated condition. The deposit is not dependent on the current distribution and hence it is almost uniform in thickness. Electroless nickel plating is far more difficult to remove chemically than conventional nickel deposits due to its superior corrosion resistance. The deposit has a good wettability and is generally hard. However, its bath control is more complex than with electroplating. The bath also has lower efficiency and higher operating costs, even without the use of electricity.
ABSTRACT: This paper investigates Phyllanthus muellerianus leaf-extract effects on steel-reinforcement corrosion in concrete immersed in 3.5% NaCl, simulating the saline/marine environment. Different concentrations of the leaf-extract were admixed in steel-reinforced concrete samples, which were immersed, with normal control, in the test-environment, while positive control samples were immersed in distilled water. Electrochemical measurements of corrosion-rate (by linear-polarization resistance instrument), corrosion-current (by zero-resistance-ammeter) and corrosion-potential (by high impedance multimeter) were obtained for assessing the reinforcing steel corrosion. Analyzed results showed that the corrosion-rate exhibited excellent correlation (R = 98.82%, Nash-Sutcliffe Efficiency = 97.66%, ANOVA p-value = 0.0006) with function of the admixture concentration and of the corrosion noise-resistance (ratio of corrosion-potential and corrosion-current standard deviations). The 0.3333% Phyllanthus muellerianus (per weight of cement) exhibited optimal efficiency, η = 97.58% ± 1.28% (experimental) or 95.33% ± 4.25% (predicted), at inhibiting concrete steel-reinforcement corrosion in the test-environment, which compares well with the positive control performance model, η = 97.96% ± 0.03%. The experimental and predicted models followed the Langmuir adsorption isotherm, which indicated physisorption as the Phyllanthus muellerianus leaf-extract adsorption mechanism on the reinforcing steel. This support suitability of the N-, S-, and O-containing and π-electron rich Phyllanthus muellerianus leaf-extract as an environmentally-friendly inhibitor for effective corrosion-protection of steel reinforcement in concrete designed for the saline/marine environment.
ABSTRACT: There has been increasing incidents of the collapse of reinforced concrete buildings in Nigeria. Many research works, suspecting the quality of concrete produced in Nigeria, have focused on concrete with few attentions on steel, perhaps because its production is usually in a more controlled environment. Over the years, many clients of building construction projects or their representatives have shown a preference for imported steel bars over the locally-produced steel bars. This research work sets out to investigate the quality of steel reinforcement produced locally and compare them with imported steel bars. The diameter of the two classes of bars available in the open market at Ilorin, Nigeria were measured and their deviations from their manufacturer's designated diameter were determined. Also, their response to the application of load and deterioration in different environments, simulated by their immersion in water, hydrochloric acid (HCL) and sodium hydroxide (NaOH), were studied. Locally-produced bars deviated more from their designated diameter than the imported bars. The imported steel bars have higher strength and experienced lower strain compared to the locally produced steel. They also showed better corrosion resistance, when immersed in distilled water and HCL, than the locally-produced steel bars. The preference for imported steel by clients of building projects is justified. There is a need for regulatory bodies, such as the Standards Organization of Nigeria (SON), to strictly monitor and penalize local steel manufacturers that engage in corrupt practices leading to significant dimensional and strength deviations from specification. This has the potential of minimizing the incidence of building collapse in Nigeria.
ABSTRACT: Zinc coatings are obtained either from cyanide, non-cyanide alkaline or acid solutions. Because of the pollution and high cost associated with cyanide, deposition from other baths is gaining importance. In order to develop a bath with an additive that could produce a quality, the coating is the motivation behind this present work which is a surface modification of Zn-8ZnO-SiO2 nanocomposite coating on mild steel surface by electrodeposition route. The influence of SiO2 on Zn-8ZnO sulfate electrolyte on the properties and microstructure of the produced nano-coatings were investigated. The SiO2 was varied from 0 to 16wt%. The microstructure characteristics of these produced series composites coating were investigated using scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS), X-ray diffraction and atomic force microscopy (AFM). The corrosion degradation properties in 3.65% NaCl medium were studied using potentiodynamic polarization technique and characterized by high-resolution optical microscope (HR-OPM). The hardness and wear of the composite coating were measured with high diamond microhardness tester and dry abrasive MTR-300 testers respectively. The results showed that the average hardness value of 142.5 and 251.2HV and corrosion rate of 0.13088 and 0.00122 mm/yr were obtained for the 0 and 16wt% SiO2 in Zn-8ZnO. The work has established that up to 16% SiO2 in Zn-8ZnO composite coating on mild steel can be used in improving the microhardness, wear loss and corrosion resistance of mild steel.
ABSTRACT: Nano-sized particle incorporation into metal matrix has gained worldwide acceptance. Al2O3, Cr2O3, and SiO2 nanoparticles have been co-deposited with Zn using the electrodeposition process to produce the advanced alloy. The coatings were characterized using SEM/EDX and XRD. The mechanical properties of the coatings were studied using microhardness indenter and dry abrasive wear tester. Zn-10 g/L Cr2O3 nanocomposite exhibited the highest microhardness of 228 HVN; Zn-5 g/L Al2O3 nanocomposite possessed the highest corrosion resistance and lowest wear loss. Zn-5 g/L SiO2 nanocomposite showed good stability against other composite coatings. The incorporation of the Al2O3, Cr2O3, and SiO2 shows grain refinement and modify orientation on Zn matrix.
Sequence diversity among bad and virus isolates infecting yam (Dioscorea spp.)
ABSTRACT : We analyzed the sequence diversity in the reverse transcriptase (RT)/ribonuclease H (RNaseH) coding region of 19 badnavirus isolates infecting yam (Dioscorea spp.) in Ghana, Togo, Benin, and Nigeria. Phylogenetic analysis of the deduced amino acid sequences revealed that the isolates are broadly divided into two distinct species, each clustering with Dioscorea alata bacilliform virus (DaBV) and Dioscorea sansibarensis bacilliform virus (DsBV). Fourteen isolates had 90-96% amino acid identity with DaBV, while four isolates had 83-84% amino acid identity with DsBV. One isolate from Benin, BN4Dr, was distinct and had 77 and 75% amino acid identity with DaBV and DsBV, respectively, and may be a member of a new badnavirus species infecting yam in West Africa. Viruses of the two main species were present in Ghana, Togo, and Benin and were observed to infect both D. alata and D. rotundata indiscriminately. This is the first confirmed report of DsBV infection in yam in Ghana and Togo. The results of this study demonstrate that members of two distinct species of badnaviruses infect yam in the West African yam zone and suggest a putative new species, BN4Dr. We also conclude that these species are not confined to limited geographic regions or specific for yam host species. However, the three badnavirus species are serologically related. The sequence information obtained from this study can be used to develop PCR-based diagnostics to detect members of the various species and/or strains of badnaviruses infecting yam in West Africa.
ABSTRACT: Surveys were conducted in 2004 and 2005 to determine the incidence and distribution of viruses infecting yams in four major yam-producing agro-ecological zones in Benin. Yam leaves collected from 69 fields and one experimental screen house were indexed for Cucumber mosaic virus (CMV), Dioscorea mottle virus (DMoV), Yam mild mosaic virus (YMMV), Yam mosaic virus (YMV) and yam-infecting badnaviruses [Dioscorea alata bacilliform virus (DaBV) and Dioscorea sansibarensis bacilliform virus (DsBV)] by enzyme-linked immunosorbent assay and immune capture polymerase chain reaction. Eighty-two percent and 66% of leaf samples tested in 2004 and 2005, respectively, were infected with CMV, YMMV, YMV and/or badnaviruses. DMoV was not detected. Yam-infecting badnaviruses were the most prevalent virus infection, detected in 45% of the total leaves sampled followed by YMV (31%), YMMV (27%) and CMV (2%). Although the occurrence of CMV was low, this is the first record of CMV in yams in Benin. Mixed virus infections were detected in 48% (2004) and 39% (2005) of the infected leaves. A mixture of YMMV and badnaviruses (DaBV or DsBV) was the most common mixed infection detected. Dioscorea alata, with a higher incidence of badnavirus infection (81%), YMMV (51%) and CMV (8%) was more heavily infected than Dioscorea rotundata.
Competition between biofuel feedstock and food production
ABSTRACT: This paper analyses the implications of the expansion of biofuel feedstock production in Malawi on local food crop production. This represents a trade-off between two provisioning ecosystem services: biofuel feedstock (i.e. sugarcane) and food crops. Specifically, we assess household-level linkages between biofuel feedstock and food crop production among farmers involved in out-grower schemes around a large-scale plantation, sugar mill, and ethanol distillery complex in Dwangwa, Central Malawi. Our analysis is based on a farm household survey that targeted sugarcane out growers (intervention group) and households not growing sugarcane (control group). We apply econometric and matching techniques to assess the impact of household participation in biofuel feedstock production on agricultural input expenditures for food crop production, land under food crops and investment in agricultural assets. In spite of limitations to establish causality, our results suggest that participation in sugarcane out-grower schemes is associated with larger amounts of land under staple food crops and higher purchases of farm inputs compared to the control group. The results further suggest that the expansion of biofuel feedstock production does not necessarily compromise household food production for those households involved in out growers’ schemes due to potentially positive intra-household linkages. We discuss under which circumstances this is possible, and whether and how other ecosystem services may be affected by sugarcane expansion.
Aflatoxins Microbial degradations
ABSTRACT: Aflatoxin (AF) contamination presents one of the most insidious challenges to combat, in food safety. Its adulteration of agricultural commodities presents an important safety concern as evident in the incidences of its health implication and economic losses reported widely. Due to the overarching challenges presented by the contamination of AFs in foods and feeds, there is an urgent need to evolve cost-effective and competent strategies to combat this menace. In our review, we tried to appraise the cost-effective methods for decontamination of AFs. We identified the missing links in adopting microbial degradation as a palliative to decontamination of AFs and its commercialization in food and feed industries. Cogent areas of further research were also highlighted in the review paper.
Contamination of fermented foods in Nigeria with fungi
ABSTRACT: This study assessed the safety and quality of some fermented foods in Nigeria. Cluster sampling was used to obtain different fermented foods: maize gruel (ogi), locust beans (iru), sorghum meal (ogi baba), dried locust beans (dried iru), African oil bean seed (ugba) and melon (ogiri) from Southwest Nigeria. Moisture content, Total Titratable Acidity, pH, and fungal diversity within each sample were determined. The identity of the isolates was established through macroscopic, microscopic and molecular biology means. The moisture content and pH of analyzed samples ranged from 12 to 56% and 3.60 to 8.08, respectively. The overall data on the mycobiota of the fermented foods revealed that total fungal loads of ugba and ogiri were 1.05 × 105 and 7.9 × 105 cfu/g, respectively. Generally, fungal isolates belonged to 17 genera including Aspergillus, Fusarium, Candida, Saccharomyces, and Penicillium. The dominant fungi detected were A. flavus and all analyzed samples were contaminated with F. verticillioides except for ogi baba. The study led to the discovery of new fungal strains and previously unreported fungal species in the selected fermented foods. The analyzed fermented foods were highly contaminated with different fungal species that could potentially be toxigenic in producing various types of mycotoxins.