Papers by Keyword: Marine Atmosphere

Abstract: The corrosion process of rare earth (RE) SPCC steel and SPCC steel in CSP in 3.5% NaCl solutions was investigated by SEM, EDS, XRD and polarization curve measurements. The results show that grain refinement can be obtained, the inclusions will be formed, and the electrochemical corrosion of microscopic region is weakened and therefore the corrosion resistance of SPCC steel could be improved by addition of RE. The rust layer of RE treated steel generated in the solution is more compact, the α-FeOOH content in rust layer is higher, and the content of activated γ-FeOOH and β-FeOOH is smaller, which are helpful to protect the steel. It also shows that current densities of SPCC steel is lower and the corrosive tendency will decrease with the addition of RE, which also makes the corrosion resistance of steel improved.

Abstract: The corrosion behaviors of pure copper were studied in initial exposure to a simulated marine atmosphere. A two-electrode cell system with two identical pure copper plates had been employed in electrochemical tests of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The copper electrodes were deposited with 70 µg cm^-2 NaCl particles and then exposed in a humidified pure air of 97% RH at 25 °C. The time-evolution of corrosion current density obtained from the cathodic polarization curves had a trend of firstly decreasing, then increasing and finally getting a relative stable stage. The EIS data showed that the transition of two time constants corrosion stage to three time constants corrosion stage. The initial atmospheric corrosion behaviors of pure copper could be divided into three stages, including rapid corrosion stage, diminished corrosion stage and balanced corrosion stage.

Abstract: Hydrogen permeation and embrittlement behavior of hot-dip galvanized steels with different sulphite sediment on surface exposed to stimulant marine atmospheric environment was investigated by hydrogen permeation current measurement using modified Devanathan-Stachurski cell, slow strain rate tensile test and scanning electron microscopy technique. The results indicated that hydrogen permeation curves were increasing along with the sediment rising gradually. On the other hand, it was found that hydrogen absorption was accelerated by the cathodic protection of scratched steel surface afforded by zinc coating. Hydrogen absorption and permeation reduced the percentage elongation after fracture of galvanized steel specimens; meanwhile, the fracture characteristics of samples fringe occurred some lacerated phenomena, i.e., galvanized steels show a higher susceptivity of hydrogen embrittlement when exposed to marine atmospheric environment with sulphite.

Abstract: Hydrogen permeation and embrittlement behavior of hot-dip galvanized steels in wet-dry cyclic simulated marine atmospheric environment was investigated by hydrogen permeation current measurement using modified Devanathan-Stachurski cell, slow strain rate tensile test and scanning electron microscopy technique. It was found that hydrogen absorption was accelerated in wet-dry cyclic environment. On the other hand, hydrogen absorption and permeation reduced the percentage elongation after fracture of galvanized steel specimens; meanwhile, the fracture characteristics of samples fringe occurred some lacerated phenomena, i.e., galvanized steels show a higher susceptivity of hydrogen embrittlement when exposed to wet-dry cyclic marine atmospheric environment.

Abstract: Hydrogen permeation current curve of galvanized steel with hot-dip zinc coating exposed to simulated marine atmosphere was measured using a modified Devanathan-Stachurski cell. Effect of temperature, humidity and coating defect on its hydrogen permeation behaviour was also investigated. The results indicated that hydrogen permeation current density and the amount of hydrogen accumulated increased evidently with temperature and humidity rising at moist environment; meanwhile, hydrogen absorption when coating defect occurred was accelerated by the cathodic protection of the exposed steel surface afforded by surrounding zinc coating.

Abstract: An ACM (Atmospheric Corrosion Monitor) type corrosion sensor, consisting of a Fe-Ag galvanic couple was developed and applied for the evaluation of corrosivity of atmospheric environments. The sensor was designed considering mass-production and good reproducibility of results, making it convenient for long-term corrosion data acquisition. Besides the sensor output, I, temperature, relative humidity (RH) were also recorded by a microcomputer. By analyzing the magnitude and time variation of I, the occurrence and duration of rain, dew and dry periods, Train, Tdew and Tdry, respectively, could be distinguished and determined. And by referencing to the empirical I-RH calibrating curve, the amount of deposited sea salt, Ws, could also be estimated. It was also found that the corrosion loss could be estimated in both indoor and outdoor sites by analyzing sensor output. Corrosivities of some kinds of exposure sites, not only outdoor environments but also indoor environments, were evaluated by using the ACM sensor.