Corrosion Behavior of a Graphite Fiber/Magnesium Metal Matrix Composite in Aqueous Chloride Solution

摘要

The corrosion behavior of a graphite fiber/magnesium composite has been studied in dilute chloride solutions by immersion, SEM, and electrochemical techniques. The composite consists of graphite fibers coated with magnesium alloy AZ91C pressed between thin foils of alloy AZ31B. Within five days immersion in 0.0001 N NaCl, severe localized corrosion develops at the edges of the material where there are exposed graphite fibers. The reaction is accompanied by visible hydrogen evolution over the entire surface and attack is through the foil covering into the underlying matrix material. Electrochemical measurements in a chloride solution of borated boric acid (pH 8.4, 1000 ppm C(-) reveal significant galvanic currents between the magnesium foil and graphite fibers. These currents increase as the surface area ratio of graphite to magnesium increases. From this work it is concluded that galvanic interaction plays an important role in the aqueous corrosion of graphite/magnesium composites.