Ce(III) Cation and Sulfate Anion Mixture as Inhibitor of Pitting Corrosion in 17-4 PH Stainless Steel
High alloy metals such as stainless steel and others are utilized in environments subjected to corrosion from the fluids, which they are in constant contact. Applications include heat exchangers, desalination plants, pipelines, tankers etc. which carry or in contact with seawater, acid, chloride and salt containing fluids etc. After time pitting corrosion is possible. This will lead to more serious forms of corrosion and eventual failure of the metal therefore it is important to inhibit the pitting corrosion process. Current methods include dissolving a pitting corrosion inhibitor into the fluid or adding corrosion inhibitors to paint or polymer coatings, which are applied to the metal. Another method is to provide a corrosion-resistant layer to the surface of the metal by incorporating cerium or other rare earth cations into the film. Current methods require a multi step process and high temperature.
The Johns Hopkins University Applied Physics Laboratory has developed and has a published patented of a method for inhibiting corrosion of alloys. This method comprises contacting at least a portion of the alloy with an aqueous solution of a salt of one or more rare earth elements selected from a group consisting of yttrium, gadolinium, cerium, europium, terbium or others: and establishing a voltage differential between an anode comprising the alloy and a cathode in the solution at an effective level and for a sufficient period of time wherein a rare earth oxide-containing coating is formed on the surface of the alloy to inhibit corrosion thereof.
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