Effect of mold on corrosion behavior of ultra high strength steels

The corrosion behavior of 300M steel, Aermetl00 steel, and ultra high strength stainless steel was investigated in the mold environment, including Aspergillus flavus, Aspergillus niger, Chaetomium globosum, Penicillium funiculosum, and Aspergillus versicolor, by scanning Kelvin probe (SKP) measurements. The growth of the mold was observed by scanning electron microscopy (SEM) and was analyzed by energy dispersive X-ray spectroscopy (EDS). The mold presents individual and cumulate growth on the specimen surface of 300M steel and the amount increases gradually, it grow individually and dispersively on the specimen surface of Aermetl00 steel and the amount increases gradually, but it shows radial and netty growth on the specimen surface of ultra high strength stainless steel and the amount increases greatly, which results in a microbial film. Some corrosion appears on the surface of all the three steel specimens after mold test. 300M steel presents the severest corrosion with wide and shallow pits, Aermetl00 steel is the next with narrow and deep pits, and corrosion resistance for ultra high strength stainless steel is the best. SKP measurements show that the mold can facilitate the corrosion process for 300M steel and Aermetl00 steel but inhibit it for ultra high strength stainless steel in some degree.