Corrosion is a very common and serious problem which has a harmful impact on the economy development of the country. Among others the application of organic paints is the most economical and efficient way to protect engineering structures from corrosion. Fluorocarbon paint is one of the most widely used resins for anticorrosion application due to its excellent corrosion resistance, chemical resistance,and weatherability. However, fluorocarbon paint also has some disadvantages restricting its application in some fields, so it is necessary to modify the fluorocarbon paint. In this article,the development history and application of the fluorocarbon paint were systematically summarized. Then various modification methods including chemical modification, physical blending, and filler modification used for enhancing the anti-corrosion performance of fluorocarbon paint were introduced. Finally, the development trend of fluorocarbon paint was forecasted.

Three high-entropy alloys Co_1.5CrFeNi_1.5Ti_0.5Mo_0.1, AlCoCrFeNiSi_0.1 and TaNbHfZrTi were prepared by arc melting. Their phase structure, microstructure and chemical composition were studied by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). A commercial alloy 690TT was used as the contrast material. The repassivation kinetics of the three high entropy alloys in high temperature pressurized water was investigated by means of electrochemical test. The results show that Co_1.5CrFeNi_1.5Ti_0.5Mo_0.1, AlCoCrFeNiSi_0.1 and TaNbHfZrTi high entropy alloys are all composed of single phase. The crystallographic structure of Co_1.5CrFeNi_1.5Ti_0.5Mo_0.1 alloy is fcc, while that of the alloys AlCoCrFeNiSi_0.1 and TaNbHfZrTi is bcc. The SEM results show that the Co_1.5CrFeNi_1.5Ti_0.5Mo_0.1 alloy showed a typical dendritic microstructure, of which the dendrite riches in Cr and Fe, but the interdendrite zone riches in Ti and Ni. There is no obvious element segregation observed in the AlCoCrFeNiSi_0.1 alloy. The TaNbHfZrTi alloy also exhibited a dendritic microstucture, of which the dendrite riches in Ta and Nb, and the interdendrite zone riches in Hf, Zr and Ti. The repassivation rates of these four alloys in high-temperature pressurized water may be ranked as the following sequence: TaNbHfZrTi>Co_1.5CrFeNi_1.5Ti_0.5Mo_0.1>690TT>AlCoCrFeNiSi_0.1.

The effect of temperature (150~285 ℃) on the electrochemical corrosion behavior of Alloy 690 in stimulated pressurized water reactor (PWR) secondary circuit water environments was investigated by means of EIS, potentiodynamic polarization curves, SEM with EDS and XPS. The results revealed that, with the increasing temperature, the free corrosion potential decreased, corrosion current density increased, passive potential region shrank, the thicknesses of oxide scales and the size of oxide particles increased. Meanwhile, the double-layer characteristics of oxide scales became more obvious, but the compactness and stability of oxide scales degraded dramatically, resulting in the deterioration of corrosion resistance and the increase of corrosion rate of Alloy 690.

3.5%(mass fraction) NaCl has been intensively used as an electrolyte for evaluating the corrosion behavior Al-alloys for decades due to the simulated sea water being close to the real service environment, particularly for the carrier-based aircrafts. But this medium has several limitations such as the lack of acid substances and the absence of pitting potentials in polarization curves for some alloys. According to Arrhenius equation, the corrosion rate is promoted by temperature. In fact, one of the most crucial factors in the corrosion of Al alloys is temperature which has a strong impact on the stability and properties of passive films. In the present work, the influence of trace Cl^- and temperature on the electrochemical corrosion of 7150-T76 Al alloy was investigated by measurements of open circuit potentials (OCP) and cyclic polarization curves as well as observation of corrosion morphology. The results showed that the localized corrosion of 7150 Al alloy was promoted by the increase of Cl^- concentration and temperature. In the solutions with relatively low temperature and low chloride concentration, pitting corrosion was the main corrosion form, while for higher temperature and higher chloride concentration, the corrosion of the alloy gradually turned to be intergranular corrosion. The presence of pit transition potential E_ptp reflects a step-wise propagation of corrosion on very narrow fronts with a sequence of active tip-passive walls. OCP shifts to the negative direction with the increase of Cl^- concentration and temperature, respectively. Moreover, OCP decreased drastically with increasing temperature above 60 ℃, indicating the chan-ge of corrosion mechanism in the temperature range from 60 to 70 ℃. In the medium of 0.1 mol/L Na₂SO₄+1 mmol/L NaCl, the free corrosion potential decreased, while the free corrosion current density increased firstly and then decreased with the increase of temperature due to less dissolved oxygen at higher temperatures. Differences between potential parameters such as ΔE₁(E_pit-E_corr), ΔE₂ (E_corr-E_ptp) and ΔE₃(E_corr-E_rep) were determined as criteria to assess localized corrosion. The value of ΔE₃(E_corr-E_rep) increased linearly with the increase of Cl^- concentration. However, ΔE₃ showed a turning point at 70 ℃ because uniform corrosion occurred at 80 ℃ as deduced from corrosion morphology. It can be concluded that ΔE₃(E_corr-E_rep) only increases linearly with the corrosion propagation at the first stage of localized corrosion.

The interface character and corrosion resistance of SiC_p/Al composites prepared with electroless nickel plated SiC particles were studied by means of XRD, SEM and EDS as well as polarization curve and electrochemical noise test. The results show that the nickel plating improves the wettability between SiC particles and aluminum matrix, increases the interface bonding strength and reduces the formation of Al₄C₃, the later is a detrimental product resulted by the interfacial reaction of SiC and the matrix. SiC_p/Al composites made of non-modified SiC particles suffered from local corrosion during immersion in 3.5%NaCl solution for the first 2000 s, and then turn to uniform corrosion. However, SiC_p/Al composites made of Ni-plated SiC particles suffered from local corrosion during the whole immersion test. In addition, the Ni-plated SiC_p/Al composites exhibited much positive free corrosion potential and higher noise resistance, therefore, implying a better corrosion resistance.

Micro-arc oxidation (MAO) coatings were fabricated on AZ31B Mg-alloy in a Na₂SiO₃-NaOH-NaF aqueous solution by varying applied negative voltages with a bipolar asymmetric pulsing power. Then the effect of the applied negative voltage on the microstructure and corrosion resistance of MAO coatings were studied by SEM and polarization curves. The results show that a corrosion resistant coating can be obtained by an applied negative voltage 40 V for a duration 10~15 min. However, the surface morphology of the MAO coating exhibited obviously many micro-cracks when the applied negative voltage is above 60 V, resulting in a poor corrosion resistance. Therefore, the value of the negative voltage and the oxidation time should be carefully matched so that to prepare a MAO coating with appropriate compactness and corrosion resistance.

The microstructure of Mg-10Gd-2.5Nd-0.5Zr (mass fraction, %) alloy after solid solution and aging treatment were characterized by means of OM, XRD, TEM and SEM. The average corrosion rate in 3.5% (mass fraction) NaCl solution was measured for 0~96 h. The results show that the microstructure of the as-cast alloy is composed of α-Mg matrix and coarse dentritic crystal β phase. After heat treatment, the β phase has experienced a course of dissolution and then precipitation, while the discontinued net-like β-phase transformed into cuboid-shaped particles due to the solution and aging treatment. The heat treatments are beneficial to the corrosion resistant of the alloy in 3.5%NaCl solution, while its corrosion rate was 0.74 mgcm^-2d^-1 for the as-cast, 0.41 mgcm^-2d^-1 for the solid solution treated and 0.35 mgcm^-2d^-1 for the aging treated ones respectively. The corrosion products of the alloy is mainly composed of Mg(OH)₂.

The inhibition effect of exopolysaccharide (EPS) extracted from Vibrio neocaledonicus sp. on carbon steel Q235 has been studied by means of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electronic microscopy (SEM). The results showed that EPS could inhibit effectively the corrosion for Q235 steel in solution of 0.5 mol/L H₂SO₄ because of that a film of Fe-EPS could formed on carbon steel during the corrosion process. The inhibition efficiency reached the maximum when the concentration of EPS was 1.0 g/L. The absorption of EPS on Q235 steel was chemisorption and obeyed the Langmuir adsorption isotherm. The composition of EPS was identified by using FTIR.

In our previous research, the corrosion inhibitory effect of marine Vibrio neocaledonicus sp. bacterium was introduced for the first time. EIS results showed that the corrosion resistance of carbon steel increased by more than sixty fold in the presence of this bacteria. The aim of this paper is the investigation of bacterial influence on the corrosion process of unalloyed copper. Different electrochemical measures (open circuit potential, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization measurements) and surface analysis techniques (field emission scanning electron microscopy (FESEM) and confocal laser scanning microscopy (CLSM)) were used. The results showed that: in the presence of bacteria, E_OCP (open circuit potential) of copper shifted to negative direction about 500 mV/(vs SCE); while the charge transfer resistance (R_ct) and the corrosion current density (I_corr) increased and decreased respectively. These results confirmed that the Vibrio neocaledonicus sp. could lessen the corrosion of unalloyed copper. CLSM images showed bacteria could adsorbed on the copper easily, but no obvious biofilm were found on the copper surface. So, it seems the corrosion inhibition of the bacteria is due to bacterial attachment in the first hours of exposure. The mechanism has been discussed in this paper.

The influence of steam on the corrosion behavior of 439 stainless steel for automotive mufflers was studied by means of cyclic hot air oxidation-immersion in condensate test and cyclic hot air oxidation-immersion in condensate-exposure to steam test as well as electrochemical measurements, SEM, XRD and pitting depth analyses. The results show that all the specimens, after cyclic hot air oxidation-immersion in condensate test and then with and without subsequent exposure to steam test, suffered from pitting corrosion with similar corrosion products. However, the specimens show lower corrosion resistance and deeper corrosion pits when they had experienced the exposure to steam test rather than those only experienced the cyclic hot air oxidation-immersion in condensate test. The exposure to steam may facilitate the growth of corrosion products and pits.

Self-assembly monolayers of hexadecane-thiol (HDT) were prepared on the surface of silver and their anti-tarnishing performance was examined by accelerated tarnish test with H₂S. Then the optimal processing parameters were acquired: the temperature is 60 ℃, the concentration of HDT is 0.1 mol/L and the experiment time is 2 h. The self-assembly monolayers were characterized also by means of water drop contact angle, polarization curve, electrochemical impedance spectroscopy and cyclic voltammetry methods. The results showed that the self-assembly monolayers of HDT on the surface of silver were compact, and the effect of anti-tarnishing for silver is excellent. Both anodic and cathodic reactions of corrosion were inhibited by HTD SAMs, the film coverage is 94.8%, and the inhibition efficiency is up to 95.9%.

The inhibition effect of Equisetum ramosissimum extractive (ERE), extracted by hot water extraction method, on the corrosion of Q235 steel in 1 molL^-1 HCl solution was investigated by means of polarization curves and electrochemical impedance spectroscopy (EIS). The results showed that ERE could effectively inhibited the steel corrosion, and acted as a mixed-type inhibitor with predominant control of the cathodic reaction. The inhibition efficiency increased with increasing dose of the extractive and was stable within the range of experimental temperature (20~50 ℃). By fitting the EIS data, it was found that the adsorption of ERE molecules on the steel surface obeyed both the Langmuir and the Dhar-Flory-Huggins adsorption isotherms. Spectroscopic analysis and scanning electron microscope observation confirmed existence of a adsorbed film of ERE on the steel surface.

Based on the data of previous analysis of groundwater samples by bore holing and the data of the field survey in Beishan area, the chemical compositions of the typical samples collected from ground waters in the desired sites were summarized in this paper. It can be drawn after a comparative evaluation of the content of the main anions and cations of ground waters that the groundwater sample collected from the third borehole in the Jiujing block can be considered as the representative of ground waters of Beishan area, therefore, which may be adopted in the near future as a medium for corrosion evaluation of candidate materials to provide a near-field chemical environment around the disposal waste container in high-level radioactive waste disposal repository of Beishan area.