Stress corrosion cracking: Characteristics, Mechanisms and Experimental study

Stress corrosion cracking (SCC) is a phenomenon in which the cracking of a metal alloy usually results from the combined action of a corrodent and tensile stress. Stresses that cause cracking can be residual or may be applied during service. A degree of mechanistic understanding of SCC will enable most metallic engineering materials to operate safely though stress corrosion cracking failures still continue to occur unexpectedly in industry. In this paper, the characteristics, mechanisms and methods of SCC prevention are reviewed. The results of experimental studies on alpha brass are also reported of which the failure mode conformed with the film-rupture and anodic dissolution mechanism

Biodegradation of Polyimide-Coated Chromium Substrates

The biodegradation of polyimide-coated chromium substrates has been investigated by electrochemical and optical techniques. All samples were sterilized prior to exposure and experiments were accomplished in either inoculated or non-inoculated (sterile conditions maintained) 0.5 M NaCl solutions. Electrochemical impedance spectra reveal that specimens exposed to inoculated solutions experience deterioration in a shorter time than samples exposed to sterile conditions. These spectra indicate deterioration of the coating and, probably, corrosion of the substrate. In addition, photographic evidence suggests that there is an effect on the polymer as a result of the presence of the microorganisms. These results strongly suggest that the polyimide- chromium system tested during this study is subject to premature breakdown in this inoculum as a result of microbial activity.link_to_subscribed_fulltex