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Steel embedded in concrete is normally in a passive state against corrosion due to a thin iron oxide layer that forms on the steel surface and remains stable in the high alkaline environment of the concrete. This protective film must be destroyed (depassivation) and this can be mainly done in two ways: by the attack of chlorides on the steel (seawater, de-icing salt, unwashed sea sand, admixtures etc.) or by carbonation. Corrosion inhibitors may be a good alternative to protection steel against corrosion due to its lower cost and easy application. Many researchers are inclined to use surface applied corrosion inhibitors and prefer to use the Cl-/inhibitor parameter as an indication of chloride inhibitor threshold level. The objective of this study was to fill the gap left by public research in developing methods of corrosion control of reinforcement in concrete by synthetic solutions to emulate concrete environment. Three inhibitors were distinguished as passivation inhibitors in real solution extract and synthetic. In this study the tests with calcium nitrite (CNI), sodium monoflurophosphate (MFP) and ethanolamine based inhibitors showed reductions in the overall rates of corrosion after the inhibitive treatments.

Purpose This paper aims to evaluate the ability of Aubepine and Molokhia extract, obtained by cathodic electrochemical treatment (CET), to protect steel rebar against attack by chloride ions in environment of reinforced concrete marine structures. The effect of Aubepine and Molokhia extract was investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. Design/methodology/approach This experimental work has achieved particularity to compare the behaviour of two types of treatment (carbon steel treated one time by Aubepine extract and one time by Molokhia extract) submitted to the presence and absence of chloride ions. Findings The results obtained show that the extract solution of the plant could serve as an effective inhibitor for the corrosion of steel. Inhibition was found to increase with increasing concentration of Molokhia extract and for Aubepine extract maximum concentration is 1 g/L. Research limitations/implications Plant extracts and traditional medicinal herbs have become important as an environmentally acceptable, readily available and renewable source for wide range of inhibitors. Originality/value Aubepine and Molokhia extract are novel green plants extract as corrosion inhibiting coating for steel embedded in concrete. Aubepine is a genus of trees in the family Rosaceae and Molokhia is the leaves of Corchorus olitorius. Flavonoids content was found in both of Aubepine and Molokhia extract as green inhibitors for corrosion of metals.

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Magnetized water (MW) is one of the most effective and economical ways to improve the properties of self-compacting concrete (SCC). Therefore, the aim of this study is to improve the fresh, mechanical, and microstructural properties of SCC using MW. For this purpose, a total of 12 mixes were produced with silica fume (SF) content (5% and 10% by weight of cement), and the mixing water passed through a permanent magnetic field (with a strength of 1.4 T) for 50, 100, and 150 cycles. Tests were performed for fresh properties (Slump flow, T50cm, V-funnel, and L-box), for mechanical properties (compressive, flexural, and tensile strength), and for microstructure properties (SEM, EDX, and TGA/DTG). The optimum result in compressive strength was achieved in the mix M8 using 5% silica fume and 150 cycles of MW. For fresh properties, the mix M4 using 150 cycles without SF had the workability enhanced by 11% compared to the control mix, and SEM and EDX tests indicated that SCC mixes prepared with MW had more C-S-H, less CH, and were denser. In addition, TGA/DTG analysis showed that the rate of hydration of mix M8 was reached by 61% at 28 days.

Purpose This study aims to synthesize a series of new anticorrosive pigments using a new technique called “core-shell”. This technique is based on depositing thin surface layer of expensive, efficient anticorrosive pigment on a cheap extender. This extender forms the bulk of the new pigments. The new pigments were constructed on cores of either waste silica fume or kaolin comprising 80-85 per cent of their chemical structure, and the ferrite shell was about of 20-15 per cent. Electrochemical studies were undertaken on two series of pigments for comparison between ferrites/silica fume and ferrites/kaolin pigment to show their performance, as the shells are different. Design/methodology/approach The different ferrites/silica fume and ferrites/kaolin pigments were characterized using different analytical and spectrophotometric techniques, such as X-ray fluorescence (XRF) and transmission electron microscopy (TEM). Immersion test and electrochemical impedance measurements were done in 3.5 per cent NaCl. Findings The tests revealed that paint films containing Sr ferrite/silica and Ca ferrite/kaolin were the most effective in corrosion prevention. Practical implications Silica fumes have a large array of uses. These pigments can be applied in various industries such as painting, wooding coating, anti-corruption coating, powder coating, architectural paint and waterproof paints. Treated kaolin can be applied in many industries besides pigment manufacture and paint formulations; it can be applied as a reinforcing filler in rubber, plastics and ceramic composites. Originality/value The new pigments are considered ecofriendly materials, because using them converts a waste product and a natural ore to useful marketable product, leading to reducing cost and saving the environment at the same time.