Abstract
Although copper steels are known to have excellent corrosion resistance to sulfuric acids, it has been found that in some cases they are attacked severely in dilute sulfuric acids with corrosion rates much higher than those in plain carbon steels. This phenomenon is termed as accelerated corrosion.Immersion tests and measurements of polarization curves of 0.3%Cu steels in 1N sulfuric acid have been undertaken in regard to this accelerated corrosion. The results of the study are shown as follows:(1) Copper steels with above 0.007%S has good corrosion resistance to sulfuric acids. However, the corrosion rates of copper steels with sulfur contents of below 0.007% and C/S ratios of above 20 in 1N sulfuric acid are several times higher than those of plain carbon steels.(2) The rates of accelerated corrosion for low sulphur-bearing copper steels are improved appreciably by heat treatments for producing the spheroidized Fe3C phase. The corrosion rates are also decreased with increasing hydrogen sulfide in sulfuric acids.(3) The corrosion rates of low sulphur-bearing copper steels increase exceedingly with time, corresponding to the increase in exchange curret densities of the cathodic reaction. Increase in cathodic exchange current densities are observed in copper-precipitated steels as well.(4) Good corrosion resistance of copper steels containing more than 0.007% sulfur seems to be due to the formation of a protective Cu2S film which is effective for retardation of the cathodic reaction.On the other hand, in low sulphur-bearing copper steels susceptible to accelerated corrosion, the copper in steel is retained or reprecipitated after dissolution on the metal surface instead of forming the Cu2S film, and increases active cathodic sites as in the case of the Fe3C phase. The resulting increase in active cathodic area with time appears to be the main cause for the accelerated corrosion.This theory might be applicable not only to the corrosion in sulfuric acids but also in both phosphoric and acetic acids.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Journal of the Japan Institute of Metals and Materials
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
