Corrosion & Environmental Degradation		Table of Contents
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	· The above discussion indicates that metallic corrosion involves both oxidation at the anode that generates a metal ion and free electrons:  M -> M+n + ne    and reduction processes that consumes the electrons at the cathode. ·The cathodic reactions listed below depend upon the nature of the corrosion environment but share the common process of electron consumption (reduction). If more than one process can occur, this will increase the overall corrosion rate. · Hydrogen ion reduction in an oxygen-free acidic environment is one possibility:      2H+ + 2e _ -> H2 (gas) · In an oxygenated acidic environment, oxygen reduction to water can occur:                            O2 +4H+ +4e -> 2H2O ·In a neutral or basic solution, hydroxyl ions may be formed by oxygen reduction:      O2 + 2H2O + 4e -> 4OH- ·Multivalent metal ions in solution may be reduced by electron transfer:                            M3+ + e -> M2+ · Metal deposition on the cathode results from the reduction of ions in solution:                           M+ + e -> M