•A typical coastal-industrial exposure environment.•Zinc corrosion influence the safe and optimal operation of nuclear power plants.•The formation of corrosion products can be divided into two different steps.•The synergy of chloride ion and sulfur dioxide.The corrosion behavior of zinc subjected to Liaoning Hongyanhe nuclear power station (a typical coastal-industrial atmospheric environment) has been investigated by weight-loss measurement, scanning electron microscopy (SEM) observation, x-ray diffraction (XRD), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The experimental results reveal that the corrosion kinetics of the corrosion of zinc in coastal-industrial atmospheric environment followed empirical equation D = Atn, and with the increase of the exposure time polarization resistance (Rp) and charge transfer resistance (Rct) increased, the corrosion rate decreased gradually. XRD, SEM and EDS indicated that the depth and width of all pits increased with time and the surface corrosion gradually transformed into a uniform corrosion. The components of the rust layers were composed of Zn5(CO3)2 (OH)6, NaZn4SO4Cl(OH)6·6H2O and Zn12(OH)15Cl3(SO4)3·5H2O. In the initial exposure period, the corrosion products was Zn5(CO3)2(OH)6, while with prolonged exposure, a two-layer structured corrosion products formed, which were comprised of NaZn4(SO4)Cl(OH)6·6H2O and Zn12(OH)15Cl3(SO4)3·5H2O, all these products were flaky-structured and compact enough to provide excellent protection.

The corrosion behavior of copper exposed in a simulated coastal-industrial atmosphere has been investigated using weight loss measurement, scanning electron microscopy, X-ray diffraction, potentiodynamic polarization and in-situ electrochemical impedance spectroscopy (EIS) with micro-distance electrodes. The results show that corrosion kinetics follows the empirical equation D = Atn. The main corrosion products are composed of Cu2O, Cu2Cl(OH)3 and Cu4Cl2(OH)6. A two-layer structure comprising a loose outer layer and a compact inner layer forms the corrosion products during corrosion process. SO2 has been found to promote the formation of Cu4Cl2(OH)6.

The corrosion evolution of weathering steel in Qinghai salt lake atmospheres as a function of exposure duration (up to 30 months) was investigated by corrosion weight gain, XRD, SEM, EDX and electrochemical techniques. The results indicated that the corrosion kinetics was closely related to the characteristics of the rust layer including composition, structure and electrochemical properties. The weight loss monotonically increased as exposure time prolonged with the fluctuations of average corrosion rate. The rust composition was mainly changed from γ-FeOOH and β-FeOOH (6 months), via β-FeOOH and magnetite (18 months), to magnesioferrite and iowaite (30 months). Correspondingly, the rust structure altered from loose and porous (6 months), via relative dense and adherent (18 months), to incompact and discontinuous again (30 months). The result of electrochemical measurements showed that rust resistance was very small, indicating that the rust layer had a poor barrier function which cannot prohibit the corrosion of steel effectively. The presence of iowaite (Mg4Fe(OH)8OCl·4H2O), which could attract Cl ions due to its special structure, was detrimental to the corrosion resistance of the rust layer and responsible for the poor weatherability of weathering steel.Highlights► A real exposure test of steel in Qinghai salt lake atmosphere was performed. ► Mg played an important role on the rust evolution process of the steel. ► The atmospheric corrosion mechanism of steel in salt lake region was proposed.

The corrosion behaviour of CortenA weathering steel has been investigated using a laboratory accelerated test that involved cyclic wet/dry conditions in Qinghai salt lake water diluted 30 times. The characteristics of the rust layers on tested samples were observed by SEM and EPMA, analyzed by IRS and XRD, and studied by polarization and EIS measurements. The weight loss was almost linear, indicating that the rust layer had no retarding effect on the corrosion process. The crystalline components of the rust layers consisted primarily of β-FeOOH, magnetite (Fe3O4) and γ-FeOOH. As the corrosion proceeded, the amount of β-FeOOH decreased while that of magnetite and γ-FeOOH increased. XRD, EDAX and EPMA indicated that the complex corrosion products magnesioferrite (MgFe2O4) and iowaite (Mg4Fe(OH)8OCl·4H2O) probably existed in the rust layer, in which case they will have had an important influence on the protectiveness of the rust layer. The results of electrochemical measurements showed that the rust layer exhibited high reduction reactivity, which facilitated the corrosion of weathering steel in the wetting process. The large rust capacitance and small rust resistance indicated that the rust layer had a loose and porous structure which provided poor protection.

A study was carried out in order to investigate the effect of contaminants and meteorological variables on the rust layer of carbon steel exposed in Shenyang urban atmosphere. Seven kinds of contaminants and twelve kinds of meteorological parameters were also registered in order to correlate the data with respect to corrosion rate and the stepwise multiple regression analysis was carried out in order to obtain the best regression model. The sum of rainfall time as well as sunshine time and the concentration of H2S could stimulate initial atmospheric corrosion of carbon steel. The initial atmospheric corrosion kinetics of carbon steel was observed to follow the cubic equation. The corrosion products were analyzed by XRD and the transformation of phases in different periods was discussed.