Effect of Surface Conditions and Specimen Composition on Hydrogen Permeation Behavior of Coated and Uncoated Steels during Wet and Dry Corrosion at a Constant Dew Point

Abstract

A wet and dry corrosion test with a constant dew point was applied to investigate the effects of scratches and specimen composition on the hydrogen permeation behavior of Zn and 55 mass% Al-Zn coated steels as well as of uncoated steel. There was an etched size controlled scratch formed on specimens with a laser machining technique. The hydrogen permeation current was observed to be independent of the specimen composition and the area of the formed scratches, the corrosion products were observed after the tests. The hydrogen permeation current of the steels with the formed scratches decreased with number of cycles of the wet and dry tests. Except in the first cycle there were no significant changes in the current with cycle number on steels without formed scratches. It was suggested that the composition, scratch, and corrosion products play an important role in the hydrogen permeation behavior during wet and dry corrosion.

Hydrogen Permeation Behavior of Scratch Formed on Zn Coated Steels in Simulated Atmospheric Corrosion Environment

“…One mechanism is Zn corrosion products around the scratch inhibit the entry of hydrogen. 18) If the area of Zn corrosion products increase with the cycle numbers, the Zn corrosion product coverage of scratch increase. This causes decline of the number hydrogen entry sites and the amount of hydrogen permeation charge.…”

“…16) However, if a scratch is formed on the Zn coating, more serious corrosion occurs and the amount of hydrogen entry increases. 17,18) Figure 1 shows a schematic representative of Zn sacrificial…”

Prevention of Hydrogen Embrittlement Using Ultra Rapid Cooling Thermal Spraying Gun

“…Delayed fracture of the high strength bolt is thought to be caused by diffusible hydrogen, which enters via the surface cathodic reactions. [8][9][10][11][12][13][14] Thus, hydrogen entry from the environment should be considered. An anti-corrosion-material coatings on a high strength steel is expected to make it possible to prevent delayed fracture due to the prevention of hydrogen entry.…”