Electrochemical Corrosion of Platinum in Hydrochloric Acid Solutions

With solutions containing Cl − ions Pt anodes dissolve as , this corrosion being quantitative for low current densities. It is known that attack by d.c. is enhanced by increasing temperature, high Cl − concentration, and high acidity. Some inhibitors, especially sulfur‐containing compounds, almost inhibit anodic corrosion. Corrosion increases when a.c. is superimposed. This effect increases with decreased frequency, being very important below 50 cps. With a 10 cps square wave, platinum corrosion is intense, and acidity and higher temperature enhance the attack. For high enough to passivate the electrode, corrosion is nil until a "critical" value of the superimposed a.c. is reached. For a little higher , corrosion increases, and with solutions of low acidity, it goes through a maximum with increasing . The oscillographic anodic and cathodic charging curves have been studied and these are discussed.