Search

• Inhibitive effect of MoO 4 2− on AA6061 aluminium alloy is related to its concentration. • Low concentration of MoO 4 2− does not play a role in corrosion inhibition. • 10 mM MoO 4 2− exhibits an optimum corrosion inhibition efficiency. • Inhomogeneous Al-Mg-Si-O(H) and Al-Ca-Mo(VI)-O(H) forms in 30 mM MoO 4 2−. Corrosion inhibition of MoO 4 2− for AA6061 aluminium alloy in simulated concrete pore solutions was investigated. Electrochemical methods were adopted to assess corrosion behaviour of AA6061 and surface characterizations were employed to obtain composition and morphology of oxide layers. Results show that low concentration (6 mM) of MoO 4 2− cannot inhibit corrosion, while MoO 4 2− of 10–30 mM effectively inhibits corrosion, which obeys Langmuir adsorption isotherm. MoO 4 2− acts as an anodic inhibitor. 10 mM MoO 4 2− exhibits an optimum corrosion inhibition efficiency. A uniform oxide layer consisting of Al-Ca-Mo(V)-O(H) complexes forms in moderate concentration of MoO 4 2− (10 mM). Inhomogeneous oxide layer consisting of Al-Mg-Si-O(H) and Al-Ca-Mo(VI)-O(H) complexes forms in high concentration of MoO 4 2− (30 mM). [ABSTRACT FROM AUTHOR]

• An optimum proportion of DSP and BTA as mixed inhibitors is proposed for carbonation-induced corrosion of rebar. • The role of DSP as a cathodic inhibitor and BTA as an anodic inhibitor are identified. • The antagonistic effect is observed in the mixture of DSP and BTA when high content of BTA is added. The corrosion inhibition of a combination of Na 2 HPO 4 (DSP) and benzotriazole (BTA) for rebar in carbonated concrete pore solutions was investigated. Electrochemical methods were adopted to assess the corrosion behaviour of rebar thermodynamically and kinetically. Also, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to detect the composition of oxide films formed on the rebar surface and the surface morphology of rebar, respectively. Results show that there exists an optimum proportion of DSP and BTA to execute the highest corrosion inhibition efficiency. The mixture of DSP and BTA acts as a mixed-type inhibitor, in which DSP behaves as the cathodic inhibitor and BTA acts as the anodic inhibitor. The adsorption of BTA obeys Langmuir adsorption isotherm. High content of BTA could compete with DSP, which leads to low inhibition efficiency. [ABSTRACT FROM AUTHOR]

Ultra-high-performance concrete (UHPC) has received increasing attention in recent years due to its remarkable ductility, durability, and mechanical properties. However, the manufacture of UHPC can cause serious environmental issues. This work addresses the feasibility of using aeolian sand to produce UHPC, and the mix design, environmental impact, and mechanical characterization of UHPC are investigated. We designed the mix proportions of the UHPC according to the modified Andreasen and Andersen particle packing model. We studied the workability, microstructure, porosity, mechanical performance, and environmental impact of UHPC with three different water/binder ratios. The following findings were noted: (1) the compressive strength, flexural strength, and Young's modulus of the designed UHPC samples were in the ranges of 163.9–207.0 MPa, 18.0–32.2 MPa, and 49.3–58.9 GPa, respectively; (2) the compressive strength, flexural strength, and Young's modulus of the UHPC increased with a decrease in water/binder ratio and an increase in the steel fibre content; (3) the compressive strength–Young's modulus correlation of the UHPC could be described by an exponential formula; (4) the environmental impact of UHPC can be improved by decreasing its water/binder ratio. These findings suggest that it is possible to use aeolian sand to manufacture UHPC, and this study promotes the application of aeolian sand for this purpose. [ABSTRACT FROM AUTHOR]

To address the limited corrosion resistance of magnesium alloys, calcium phosphorus coatings are frequently applied to their surfaces as a means of compensating for this drawback. However, cracking of traditional calcium phosphorus coatings greatly affects their protective properties. In this research, a novel CaHPO 4 ·2H 2 O (DCPD) and CaCO 3 composite coating with no cracks was obtained via a chemical conversion method assisted by ultrasound. DCPD coatings were also fabricated in the same method. All the coatings possess excellent adhesion strength to the substrates. In addition, electrochemical tests results show that the elimination of cracks greatly improves the anticorrosion performance of composite coatings. Optimization of the bath constituents resulted in a reduced reliance on interfacial electrochemical reactions during the co-deposition process, which plays a critical role in attaining the high-quality coating. This innovative composite coating provides a promising avenue for surface treatments of magnesium alloy concrete formwork. • A composite CaHPO 4 ·2H 2 O/CaCO 3 coating via ultrasound treatment on Mg alloy was prepared. • The elimination of cracks in the composite coating significantly enhanced the corrosion resistance. • The Ca/P/C-Ca composite coating shows regrowth performance. [ABSTRACT FROM AUTHOR]

The corrosion inhibition of EDTA-Ca for mild steel in chloride-contaminated concrete pore solution, with EDTA-Na as comparison, was investigated via several electrochemical methods and surface characterizations. Results show that corrosion inhibition efficiency of EDTA-Ca is higher than that of EDTA-Na. Corrosion inhibition efficiency increased with an increase in EDTA-Ca concentration while decreased with the increased EDTA-Na concentration. EDTA-Ca adsorbs physiochemically on surface of mild steel which obeys Langmuir isotherm, while adsorption of EDTA-Na is physical obeying Freundluich isotherm. A much thinner and more compact oxide film with higher Fe2+ content formed in the presence of EDTA-Ca compared to EDTA-Na. The availability of coordinate bonds for chelation in EDTA-Ca or EDTA-Na plays a critical role in determining the corrosion inhibition efficiency. • Enhanced corrosion inhibition of EDTA-Ca than EDTA-Na for mild steel in concrete pore solution was obtained. • Inhibition efficiency of EDTA-Ca increased with increased concentration. • EDTA-Na adsorbs physically while adsorption of EDTA-Ca is physicochemical. • EDTA-Ca possibly favours formation of insoluble EDTA-Ca-Fe(II) complexes on steel. [ABSTRACT FROM AUTHOR]

• Passivation film thickness of rebar in alkali-activated pore solution were obtained. • Composition of passive film for two kinds of rebars were characterized by XPS. • The protective ability of passive film was deeply analyzed by molecular dynamics. The study on the properties of passive films in alkali-activated slag cement can provide a theoretical basis for the development and application of low-carbon and environmental friendly concrete materials. In this paper, the passivation behaviour of anti-corrosion rebar (AR) and normal reinforcing steel (NR) in sulfur-free simulated pore solutions of alkali-activated slag cement pastes was investigated using electrochemical, microscale techniques and molecular dynamics modelling. Results showed that the formation time, composition and thickness of the passive film were affected by the types of simulated pore solutions. Molecular dynamics further elucidated the reason for difference in the protective ability of passive film in three types of simulated pore solutions. The results of protection capability of two kinds of rebar obtained from molecular dynamics were consistent with those of electrochemical impedance spectroscopy (EIS). [ABSTRACT FROM AUTHOR]