Evaluation of synergic methods for corrosion protection of reinforced steel

Purpose This study aims to evaluate the effect of pH on the reinforced concrete steel protection for rebars coated with paint formulations containing talc and free from it. As the presence of talc in paints can offer high pH which cordially affects the protection behavior of the coated rebars. Additionally, this study includes evaluating the durability of concrete mixes in presence of some replacements of ordinary cement such as meta-kaolin (MK) and ground granulated blast furnace slag (GGBFS). Design/methodology/approach Two paint formulations were prepared containing the same ingredients except that (P1) is free from talc and (P2) contains talc. The anticorrosive behavior of painted steel in the blended concrete mixes containing MK and GGBFS was studied by using different electrochemical techniques in chloride solution. The concrete durability was evaluated by the means of compressive and bond strength beside chloride permeability. Different concrete mixes containing mineral groups or pozzolanic materials were prepared by replacing (10, and 30%) GGBFS and (5, 10 and 15%) MK as binary from cement CEM I with (w/b) 0.45 with superplasticizer ratio (SP) 2% of the binder Findings It was found that the presence of talc, in spite of its ability to offer high pH, has affected positively the corrosion behavior of reinforced concrete steel by forming a complex with concrete even if it is present in paint formulation and not free in the medium. Originality/value The results revealed that concrete blended with (30% GGBFS and 10% MK) with coated rebars with P2 containing talc showed the highest corrosion protection performance in addition to modified permeability and compression resistance.

Effect of SRB and Applied Potential on Stress Corrosion Behavior of X80 Steel in High-pH Soil Simulated Solution

The effect of SRB and applied potential on the stress corrosion sensitivity of X80 pipeline steel was analyzed in high-pH soil simulated solution under different conditions using a slow strain rate tensile test, electrochemical test, and electronic microanalysis. The experimental results showed that X80 pipeline steel has a certain degree of SCC sensitivity in high-pH simulated solution, and the crack growth mode was trans-granular stress corrosion cracking. In a sterile environment, the SCC mechanism of X80 steel was a mixture mechanism of anode dissolution and hydrogen embrittlement at −850 mV potential, while X80 steel had the lowest SCC sensitivity due to the weak effect of AD and HE; after Sulfate Reducing Bacteria (SRB) were inoculated, the SCC mechanism of X80 steel was an AD–membrane rupture mechanism at −850 mV potential. The synergistic effect of Cl− and SRB formed an oxygen concentration cell and an acidification microenvironment in the pitting corrosion pit, and this promoted the formation of pitting corrosion which induced crack nucleation, thus significantly improving the SCC sensitivity of X80 steel. The strong cathodic polarization promoted the local corrosion caused by SRB metabolism in the presence of bacteria, whereby the SCC sensitivity in the presence of bacteria was higher than that in sterile conditions under strong cathodic potential.

Alkaline Agarose Gel Electrophoresis

Alkaline agarose gels are run at high pH, which causes each thymine and guanine residue to lose a proton and thus prevents the formation of hydrogen bonds with their adenine and cytosine partners. The denatured DNA is maintained in a single-stranded state and migrates through an alkaline agarose gel as a function of its size. Other denaturants such as formamide and urea do not work well because they cause the agarose to become rubbery.

Fungicidal effects on cement composites with recycled glass from photovoltaic panels

This research was focused on the effects of micromycetes on cement composites with 100% replacement of natural aggregate by the recycled glass from photovoltaic panels. The experiment was performed on samples of small beams measuring 40 x 40 x 8 mm (length x width x height) and cement crumbling with recycled glass from photovoltaic panels in percentages representing 10%, 20% and 40%. The representatives of the selected micromycetes were Aspergillus niger, A. clavatus, Penicillium glabrum, Cladosporium sp. and Zygomycetes sp. Biocorrosion causes changes in the properties of the material, mainly as a result of the action of microorganisms. Due to their large production of acids and enzymes, micromycetes are an important part of microscopic consortia involved in biocorrosion. This experiment focused on evaluating the effect of micromycetes on cement composites – solid structure and crumbling, with 100% replacement of natural aggregate with photovoltaic glass recyclate. The results show a high growth of biomass on solid composites, while on cement crumbling, the growth was minimal due to high pH value. Longer monitoring time was used in case of adaptation to the environment.

A study of inline chemical coagulation/precipitation-ceramic microfiltration and nanofiltration for reverse osmosis concentrate minimization and reuse in the textile industry

Reverse osmosis concentrate (ROC) is one of the major drawbacks in membrane treatment technologies specifically due to the scale-forming ions. It is important to remove these ions from ROC to enhance total water recovery and reuse in the textile industry that is the largest water-consumer and polluter industry. In this work, coagulation/high pH precipitation (CP) integrated with ceramic microfiltration (CMF) was studied as a pretreatment method followed by nanofiltration (NF) to increase the efficiency of water recovery. To prevent organic fouling, ferric chloride (FeCl3) was applied at a concentration of 3 mM, and ceramic membranes were used for the removal of non-precipitating crystals and/or suspended solids (at high pH) before the NF processes. The CP-CMF method successfully removed calcium (Ca2+), magnesium (Mg2+), silica (SiO2), and TOC up to 97, 83, 92, and 87% respectively, which resulted in higher performance of the NF process. Moreover, this method provided higher flux at lower pressure that ultimately increased overall water recovery of the NF process to achieve near-zero liquid discharge (n-ZLD). A cost-benefit estimation showed that a high-quality effluent (COD<5 mg/L; conductivity 700<μS/cm; negligible residual color) can be generated and recycled in the textile industry at an economical cost (approximately 0.97 USD/m3). Therefore, ROC minimization and water recovery can help to achieve n-ZLD using CP-CMF/NF method.