Mechanisms for pitting corrosion in alloy N04400 as revealed by imaging XPS, ToF‐SIMS and low‐voltage SEM

Abstract

Abstract Imaging XPS has been used to determine the distributional patterns of corrosion products of different chemistry on a nickel–copper alloy surface that has been subjected to pitting corrosion. Separate regions within corrosion pits can be identified with chemical processes that are suggested to be anodic and cathodic in nature. The anodic processes are indicated by a thin layer of cuprous oxide covering the base alloy, suggesting the preferential dissolution of nickel. Areas undergoing a cathodic process are indicated by the deposition of nickel as an oxide or hydroxide. Adjacent regions also were studied by XPS and characterized further by low‐voltage SEM/energy‐dispersive x‐ray imaging and time‐of‐flight SIMS techniques to obtain confirmatory and complementary information. Typically, the anodic and cathodic areas were tens of microns in size. Copyright © 2002 John Wiley & Sons, Ltd.