Rust spots and tarnish on the surface of silver coin were the two major issues in the world and neither one had been explained clearly. This article was to summarize the research progress of silver coin tarnish and its mechanism in recent years. The overview focused on the effect of corrosion media including oxygen, hydrogen sulfide, sulfur and sulfur dioxide on silver tarnish. At one time, the effect of environmental factors, such as ambient humidity, temperature, illumination, etc., was also introduced. The corrosion products on the surface of silver coin in atmospheric environment were analyzed and the outlook of anti-tarnish for silver coin was proposed.

Alternating current (AC) corrosion on buried pipelines has drawn much attention. Current status of the researches is reviewed in this article. The understanding of AC corrosion is mentioned. Characteristics, mechanisms, and mitigations of AC corrosion and the evaluation methods for AC corrosion risk are concluded. Finally, the issues for further investigations are proposed.

The Ni-P/nano-Al₂O₃ composite coating on Q235 steel was prepared by pulse electroplating, the composite coatings were heat-treated at temperature of 200-400 ℃. The microstructure of the composite coatings was identified by X-ray diffraction, the corrosion behavior of the composite coatings in 3.5% NaCl and 10% H₂SO₄ solutions was studied by the linear polarization measurements and scanning electron microscope (SEM). The results show that nano-Al₂O₃ particles retard precipitating of Ni₃P phase in composite coating, the crystallization temperature of the composite coating is higher than that of Ni-P alloy coating. The as-deposited and after 300℃ heat-treated composite coatings revealed better corrosion resistance in two corrosive solutions. The corrosion resistance of after 400℃ heat-treated composite coatings decreased. The corrosion behavior is pitting corrosion.

Currently there is a demand to transport crude oil and gas by pipeline at a higher operating pressure in order to increase the capacity. For the investment reduction of long distance crude oil and natural gas pipeline project, the X100 grade ultrahigh strength pipeline steel will be adopted. Stress corrosion cracking (SCC) in pipeline is an important problem that threatens the safe operation of oil and gas transmission. Therefore, it is necessary to study SCC behavior of X100 pipeline steel in a standard near-neutral pH solution, NS4 solution. In this paper, constant loading tests of X100 pipeline steels were conducted at open circuit condition in deaerated NS4 solution. The results show that X100 pipeline steel under constant load in deareated NS4 solution exhibit transgranular stress corrosion cracking behavior. Even though the applied stress was less than the yield stress of X100 pipeline steel, stress corrosion cracking also occurred. It was found crack initiated at the interface of bainite phase and ferrite phase, M/A constituent and matrix, carbide and ferrite in bainite.

Two electrodeposited Ni matrix composite coatings were prepared; one was Ni-11Cr-3Al (by mass%) prepared using nano-sized particles of Cr and Al and the other was Ni-11Cr-7Al composite prepared using micron-sized particles of Cr and Al. Compared with the electrodeposited micron-composite (EMC) Ni-11Cr-7Al, the electrodeposited nanocomposite (ENC) Ni-11Cr-3Al exhibited much homogeneous distribution of Cr and Al particles, because of an approximately 25-fold decrease in interparticle spacing. The significantly shorter interparticle spacing allowed the ENC Ni-11Cr-3Al to grow a continuous Cr₂O₃ layer first and then an Al₂O₃ layer underneath during a very short stage of oxidation. This is the fundamental reason for the result that the ENC, although it had a lower content of Al, was oxidized slower than the EMC Ni-11Cr-7Al during oxidation in air at 900℃. The size effect of the Cr and Al particles on the oxidation behavior of the electrodeposited Ni-Cr-Al composite coatings is discussed in detail.

Al₂O₃-13%TiO₂ and Cr₂O₃•5SiO₂•3TiO2 erosion-resistant ceramic coatings were deposited on Al-bronze alloy using plasma spraying process. The morphologies of the two coatings were investigated by means of scanning electron microscope (SEM) and laser scanning microscope (LSM). Microhardness and adhesion strength have been evaluated, respectively. The corrosion behavior of two coatings in 3.5% NaCl solution were characterized by potentiodynamic polarization and electrochemical impedance spectroscopy. SEM analysis of corroded surface and weight loss technique were used to study the erosion-corrosion of coated samples and uncoated sample in flowing seawater. The results indicated that Cr₂O₃•5SiO₂•3TiO₂ coating has a much dense microstructure and the laminar microstructure was not obviously observed. The corrosion behavior of ceramic coatings was mainly related to the porosity of the coatings. Due to higher microhardness and adhesion strength, the weight loss of Cr₂O₃•5SiO₂•3TiO₂ coated sample was nearly 1/9 of that of uncoated one, indicating better resistance to erosion-corrosion in flowing seawater than Al₂O₃-13%TiO₂ coating.

High strength steel wires are susceptible to hydrogen induced fracture. It is generally considered that fracture will occur when a critical hydrogen concentration at the location of the stress peak was reached by accumulation, and that the time to fracture was related to the stress assisted hydrogen diffusion process. Residual stresses generated by cold drawing play an important role in hydrogen accumulation. However, plastic strain also has significant effect on the hydrogen diffusion process. In this paper, a numerical model was developed for calculating the accumulated hydrogen concentration in cold drawn steel wires, taking into account the driving effect of both the residual stress and strain generated by cold drawing on hydrogen transport. First, a finite element model, using the code ABAQUS, was developed to reproduce the drawing process, and to determine the residual stress and strain profiles. The results showed that the drawing process generated a residual stress state in the wire with significant tensile stresses at the surface in the axial and hoop directions. Finite difference method was used to solve the stress-strain assisted and stress-only assisted hydrogen diffusion equations. The hydrogen concentration accumulated in stress-strain assisted case is lower than that in stress-only assisted case in shorter time, that was slowed down by plastic strain due to diffusion. However, after long exposure time, the hydrogen concentration was much higher than that in stress-only affected case. The results in this paper prove the relevant role of residual plastic strain in hydrogen diffusion in cold drawn wires, as well as the residual stress.

Accelerative corrosion experiments were conducted on Q235 carbon steel in seashore salt soil in order to determine acceleration ratios and dynamic correlation coefficients. The experimentation utilized constant temperature and water content, various temperatures, and different water contents to calculate mass loss of steel samples in the lab; also, samples were put in the ground one meter deep, so as to perform addition analysis in the field. The results indicated that the acceleration ratio increased when the temperature increased; in addition, at the same temperature, the acceleration ratio was largest when the water content was 10%, then progressively lessened for the 10 %~30 % water content; for the 20 % and 30 % moisture levels, the values flattened and reached a minimum. For a constant temperature, the dynamic correlation was lower for low water content accelerative experiments, and higher for moderate and high water contents. At 50℃, the correlation coefficients were higher than those at 70℃. For these experiments, 70℃ and 20 % water content, achieved optimal results of the acceleration ratio and correlation coefficients.

In order to utilize effectively massive and discrete materials corrosion data, a data sharing platform of material corrosion is proposed for scientific research. It is based on platform engine, and adopts Meta Data driven based on XML（extensible markup language） to implement the unified storage and conversion of different structures, types of materials corrosion data. Intelligent agent and middleware technologies are used to management and operation the heterogeneous databases. The user-role-privilege is adopted to implement user's security management. The four-layer architecture including application layer, integration layer, transform layer, and data layer is used to implement data security. A demo system is used to prove the feasibility of platform. The platform has characteristics of sharing, security, scalability and openness.

Naphthenic acid corrosion (NAC), sulfur corrosion (SC) and their interaction on Cr5Mo carbon steel were studied by mass loss test using a spinning coupon inside a heated autoclave at 280℃. The test mixture with different level of sulfur content and total acid number were prepared by pure naphthenic acid, lauryl mercaptan and low sulfur white oil. It was found that the increasing sulfur content can accelerate the NAC dramatically when the sulfur content lower than 2.0 mass%. However, the boost effect of mercaptan to NAC decreased quickly when the sulfur content is higher than 3.0 mass{\%}, which could be attributed to the formation of protective Fe₇S₈/Cr₅S₈ layer confirmed by scanning electron microscope（SEM）, energy dispersive X-ray（EDX） analysis and X-ray diffraction（XRD） analysis. Surprisingly, high content of lauryl mercaptan could even inhibit the NAC in case of higher TAN  (>15.0 mg/g KOH), and the increasing content of TAN could enhance the inhibition of mercaptan on NAC. In contrast, the dimethyl sulfoxide（DMSO）exhibits stronger inhibition ability than mercaptan in case of high TAN in the test mixture.

A new corrosion inhibitor N,N-diethylammonium O,O' -dicyclohexyldithiophosphate (EDCDP) has been synthesized. The inhibition effect of EDCDP against the corrosion of Q235 steel in H₂SO₄ solution was studied by mass loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. mass loss shows that the inhibition efficiency is up to 97.32 % at the inhibitor concentration of 100 mg/L in 5 % H₂SO₄ solution. The adsorption of EDCDP on Q235 steel surface obeys the Langmuir's isotherm. Polarization curves indicate that the EDCDP is a mixed type inhibitor. The inhibition efficiency of EDCDP is less impact by concentration of H₂SO₄, temperature and immersion time.

The effect of sulfate - reducing bacteria (SRB) on corrosion behavior of Cu-Ni-Sn alloy were studied using open circuit potential, polarization curve and electrochemical impedance spectroscopy (EIS) methods. Scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) were utilized to investigate the corrosion morphologies of Cu-Ni-Sn alloy. The open circuit potential of the alloy in condition with SRB decreased from -275 mV to -750 mV and nearly 650 mV lower than that of which without SRB (-100 mV). SEM results showed that an uneven biofilm occurred on the alloy surface and there were pitting corrosion and crevice corrosion. EDS analysis indicates that denickelification and detinning corrosion occurred and the corrosion products were copper and nickel sulfide. Therefore, the corrosion of Cu-Ni-Sn alloy accelerated under the biofilm of SRB.

The effect of hydrogen on the mechanical properties for 2(1/4)Cr-1Mo steel for hydrogenation reactor wall-materials was investigated at the simulated service condition of hydrogenation reactor. The crack propagation rate da/dN and the threshold value Δ_th at low frequency fatigue were calculated. Hydrogen distribution of crack tip were measured. The results showed that hydrogen content related to stress field. The higher the stress, the higher the hydrogen content. The residual cycle life for hydrogenation reactor was calculated, supposing surface crack exists in reactor.

The corrosion behavior of two ferritic-martensitic steel K1 and K2 exposed to supercritical water at 500℃ and a pressure of 25 MPa for exposure times of 200 h, 400 h, 600 h, 800 h, 1000 h was investigated. The results from scanning electron microscope/energy dispersive spectroscopy (SEM/EDS) analyses indicated that the oxide scale exhibits typical duplex oxide structure, in which the scale is composed of an outer layer of more porous magnetite，and an inner layer of iron chromium spinel. The results of corrosion dynamic manifest that two materials follow the parabolic rule, and the corrosion oxidation rate of K2 steel is faster than that of K1 steel, but the gap within 5%.