Corrosion of reinforced concrete is one of the main factors affecting the durability of concrete structures, therefore, the inspection and monitor of corrosion of the reinforced bar within concrete structures is an important measure for safety of the structures. This article describes several electrochemical and physical methods for inspecting and monitoring the corrosion of reinforced bars in terms of their principle and characteristics.This paper also introduces the present situation of their application in various fields.

Several typical nitrogen alloyed dual stainless steels were introduced in the highlight of their application in wet processing of phosphoric acid production and of their performance such as mechanical property and corrosion resistance etc. In general, the nitrogen alloyed stainless steels possessed comprehensive performance suitable to the applications in wet processing of phosphoric acid production; therefore, it is worthy to pay much attention to R&D of such steels in terms of saving nickel.

The special alloys, those are considered as the candidate materials of pumping system for circulating and concentrating of sulfuric acid, are reviewed in the article. The system is one of the key facilities for the recovery of the waste sulfuric acid in the production process for titanium dioxide, and is suffered from intensive corrosion and/or erosion-corrosion in solid particles containing dilute sulfuric acids at rather high temperatures. The application feasibility of the alloys was carefully analyzed in terms of their performance such as mechanical property, hardness, brittleness, especially resistance to corrosion and erosion-corrosion etc. The relevant technical data of the alloys were also presented in the article.

The cavitation erosion behavior of a cobalt-containing austenitic stainless steel was studied in comparison with 304ss. The strength and the cavitation mass loss of the steel were measured. The morphology and microstructure of the steel after cavitation erosion were observed by SEM and TEM. The results reveal that, compared with 304ss, cobalt-containing steel has higher strength, and longer incubation time to cavitation erosion, which indicates an improved cavitation erosion resistance for the Co-containing steel. A morphology with equilateral friangles was observed on the Cr-Co-Ni-Mn steel surface after cavitation erosion by SEM, ε-martensite induced by the deformation of cavitation corrosion layer was observed by TEM and α-martensite was also found. This kind of deformed microstructures can absorb strain energy and thus leads to an improved cavitation erosion resistance.

Several electrochemical means such as Tafel-, EIS- and Mott-Schottky-measurements were used to investigate the semi-conducting property of the passive film formed on Cu-Ni alloy coatings in 1 mol/L NaOH solution. At the same time, the Point Defect Model (PDM) was adopted to calculate the acceptor density, flat potential and vacancy diffusion coefficient in the passive film formed on Cu-Ni alloy coatings. The results show that the passive films formed on Cu-Ni coatings display p-type semi-conducting characteristics, corresponding to a preponderance of metal vacancies (over oxygen vacancies and interstitials) in the barrier layer. With the increase of Cu, the flat potential moves toward positive, the acceptor density and impedance of passive films decrease, the negative moving of the film formation potential causes an increase in acceptor density. The calculated value obtained for D^o is about 10^-14 cm²/s.

By means of sol-gel process coupled with ultrasonic, hydrophobic silica particles have been synthesized by using hydroxyl-terminated polydimethylsiloxane (PDMS-OH) and tetraethoxyorthosilicate (TEOS) as precursor and ammonium hydroxide as catalyst, with and without addition of a crosslinking agent, 3-glycidoxypropyltrimethoxysilane (GPTMS). The molar ratio of tetraethoxysilane (TEOS), ethanol, basic water, H²O was kept constant at 1 : 73 : 192 : 7.6 and the molar ratio of PDMS-OH/TEOS (M) varied from 0.27 to 0.675. The particle size of the synthesized silica is 167 nm measured by SEM and the organic GPTMS modification was confirmed by infrared spectroscopic studies, incorporation of which leads to decrease of the stability of the composite. Then samples of limestone were coated with a paint consisted of the hydrophobic silica particles synthesised with a precursor (PDMS-OH) : (TEOS)=0.675, that coating showed a contact angle up to 152° and a satisfied corrosion resistance to cyclic spraying with dilute sulfuric acid.

By means of surface mechanical attrition treatment (SMAT), a nanocrystalline (NC) surface layer was obtained on Cu-10Ni Alloy. The electrochemical corrosion behavior of three samples, i.e. the original coarse grain ones, the SMAT for 60 min ones, and the ones SMAT for 60 min plus annealed at 200℃ for 6 h, was investigated by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques in 0.05 mol/ L Na²SO⁴ + 0.05 mol/L H² SO⁴ solution. The result showed that the corrosion potential of the SMAT Cu-10Ni Alloy shifted to a more negative value with respect to the un-treated alloy claerly Implying a decrease of the corrosion resistance of Cu-10Ni alloy after SMAT. However, the SMAT alloy exhibited passivation behavior to certain extent in its polarization curve.

The corrosion behavior of the hot-dip 55%Al-Zn-1.6%Si alloy coating steel sheet and a commercial hot-dip Zn coating steel sheet in the 5% NaCl aqueous solution has been comparatively studied by the salt fog corrosion test and electrochemical impedance spectrum (EIS). Optical microscope (OM) and Scanning Electron Microscope (SEM) have been employed to observe the surface characteristics of the corroded steel sheets after removel of the corrosion products. The results indicate that, the corrosion resistance of hot-dip 55%Al-Zn-1.6%Si alloy coating is 2.5 times higher than that of commercial hot-dip Zn coating. The corrosion of the commercial hot-dip Zn coating is mainly controled by the diffusion process on the electrode surface, while that of hot-dip 55%Al-Zn-1.6%Si alloy coating is mainly controlled by the charge transfer process.

By means of cyclic voltammetry, the electrochemical behavior of copper electrode in non-cyanide alkaline electrolyte containing 1-hydroxyethylene-1, 1-diphosphonic acid (HEDPA) as a complexing agent was investigated. Then X-ray photoelectron spectroscopy analysis was carried out for the formed oxidation products on copper electrode by different potentials. The results showed that in the 1-hydroxyethylene-1, 1-diphosphonic acid (HEDPA) baths, the first oxidation peak represents a diffusion-controlled process corresponding to the formation of Cu²O. The second and the third oxidation peaks represent the formation of CuO and CuO/Cu(OH)² compounds respectively.

In the long-term corrosion process, the rust layer formed on the low carbon hull steel may affect its corrosion behavior. The influence mechanism of the outer rust layer on the hull steel corrosion behavior is unclear. A certain type of low carbon steel was selected to soaked in 3mass% NaCl solutions for one year, then of which the electrochemical corrosion characteristic was studied by electrochemical methods before and after removal of the formed outer rust layer. The corrosion resistance before and after the removal of the outer rust layer was compared, and the effect of the outer rust layer on the corrosion of the rust steel was analyzed by use of linear polarization, AC impedance spectroscopy (EIS) and electrochemical noise (EN). The morphology, phase constituents and elemental distribution of the corrosion products formed on the rust and base steels were characterized by EPMA and XRD respectively, then the relevant corrosion mechanism was discassed. The results show that, the corrosion resistance of the steel decreased and the corrosion rate increased after removal of outer rust layer; the removal of the outer rust layer may facilitate the oxygen inward-transportation thereby affecting the electrode process on interface of the rust layer/metal matrix.

A Ag/4.0 mass%Cr²O³ composite film was fabricated on Cu substrate for application as electric contact through a two-step process: prior fabrication of a Ag/2.4Cr composite coating through co-electrodeposition of Ag with Cr nanoparticles (mean size: 30 nm) and then oxidation at 500 ℃ in air. The results showed that the Cr particles in the Ag/2.4Cr composite coating were locally and diffusionlessly oxidized. Compared to the conventional Ag/Me^xO^y type electric contacts (such as Ag/12CdO) fabricated by internal oxidation of the corresponding Ag-Me alloys (e.g., Ag-10.5Cd) reported, the Ag/4.0Cr²O³ composite film has similar density and electrical resistivity, but a higher hardness.