Corrosion of Metals: Electrochemical Reactions

Metallic corrosion is ordinarily ______ electrochemical

Oxidation is the loss of the metal atom’s ______ electrons

During ______ (which occurs at the cathode), these electrons are transferred to at least one other chemical species

The character of the corrosion environment dictates which of several possible ______ reactions will occur

Not all metals ______ with the same degree of ease, which is demonstrated with a galvanic couple

The magnitude of the electric ______ that is established between anode and cathode is indicative of the driving force for the corrosion reaction

The standard emf and galvanic series are simply rankings of metallic materials on the basis of their tendency to ______ when coupled to other metals

The galvanic series consists of the relative ______ of metals and alloys in seawater

Metallic Corrosion

Metallic corrosion is an electrochemical process involving both oxidation and reduction reactions.
Oxidation occurs at the anode, resulting in the loss of valence electrons from the metal atom, which may form an insoluble compound or go into the corroding solution.
Reduction occurs at the cathode, where the electrons are transferred to at least one other chemical species.
The corrosion environment dictates the type of reduction reaction that will occur.

Galvanic Couple

A galvanic couple demonstrates the varying degrees of ease with which metals oxidize.
When two metals are in an electrolyte, one metal (the anode) corrodes, while a reduction reaction occurs at the other metal (the cathode).
The electric potential established between the anode and cathode indicates the driving force for the corrosion reaction.

Standard Emf and Galvanic Series

The standard emf series ranks metallic materials based on their tendency to corrode when coupled to other metals.
The ranking is based on the magnitude of the voltage generated when the standard cell of a metal is coupled to the standard hydrogen electrode at 25°C (77°F).
The galvanic series ranks the relative reactivities of metals and alloys in seawater.

Half-Cell Potentials

Half-cell potentials in the standard emf series are thermodynamic parameters valid only at equilibrium.
Corroding systems are not in equilibrium, so these potentials are not directly applicable.
The magnitudes of these potentials do not indicate the rates at which corrosion reactions occur.

Learn about the electrochemical process of metal corrosion, involving oxidation and reduction reactions. Understand how the corrosion environment affects the reaction.