Passivity (forming passive layers inhibiting the corrosion process on the surface of the metal, including thermodynamically active metals).Thus, Pourbaix diagrams introduce the concept of the following three states of metals, depending on the potential in the given aggressive medium and the determination of its corrosion behavior: To show which environmental pH and potential changes will reduce or prevent corrosion.To make a basis for estimation of the corrosion product compositions at various pH and potential combinations.To show the directions of the various reactions at given pH and potential.The main objectives of the Pourbaix diagrams are: By altering the pH and potential to the regions of immunity and passivation, corrosion can be controlled. The information in the diagrams can be beneficially used to control corrosion of pure metals in the aqueous environment. Pourbaix diagram is used to determine the stability of metals or alloys at a given electrode potential and pH. These diagrams are plotted on the basis of Nernst equation which is entirely derived from thermodynamics. Pourbaix diagram is also known as potential-pH diagram or EH-pH diagram or equilibrium diagram or E-pH diagram. Pourbaix diagrams have several uses including corrosion in metals. These diagrams are available for over 70 different types of metal. A pourbaix diagram provides information about the stability of metal as a function of pH and potential.
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