Pourbaix Diagrams

A handful resources of Pourbaix diagrams is available in this post with high quality. This diagram is a kind of phase diagrams which is named after Marcel Pourbaix (1904–1998), the Russian-born, Belgian chemist who invented them. In chemistry, A Pourbaix diagram provides information about the stability of a metal as a function of pH and potential. These diagrams are available for over 70 different metals. Pourbaix diagrams have several uses, including in corrosion studies. A Pourbaix diagram is also known as a potential/pH diagram, equilibrium diagram, EH-pH diagram, a pE/pH diagram on an E-pH diagram. Take a look at the following first example of the Pourbaix diagram for cobalt-water system.

pourbaix diagram cobalt
image via metallographic.com

Pourbaix diagrams provide information on three states of metals: corrosion or the active state, passivity or forming passive layers inhibiting the corrosion process on the surface of the metal, and immunity or the thermodynamic stability. This diagram has some characteristics: the horizontal lines represent electron transfer reactions (they are pH-independent, but potential-dependent); vertical lines are potential-independent but pH-dependent and not accompanied by any electron transfer; sloping, straight lines give the redox potentials of a solution in equilibrium. This equilibrium indicates electron transfer as well as pH; the diagram is computed for the equilibrium conditions at 77°F (25°C). More examples for the iron, mangan, and nickel Pourbaix phase diagrams are provided below.

pourbaix diagram iron
image via wow.com
pourbaix diagram mangan
image via wikibooks.org
pourbaix diagram nickel
image via etallographic.com

This diagram is usually used for many purposes: to show the directions of the various reactions at given pH and potential; to make a basis for estimation of the corrosion product compositions at various pH and potential combinations; and to show which environmental pH and potential changes will reduce or prevent corrosion. Posted below are the Pourbaix diagrams for selenium, mangan, and Zn.

pourbaix diagram Zn
image via wikimedia.org
pourbaix diagram selenium
image via akitarescueoftulsa.com
pourbaix diagram potential
image via digplanet.com
pourbaix diagram potential
image via digplanet.com

Get all these diagrams as your teaching or learning resources in studying about the Pourbaix principle. More educational and resourceful diagrams are available in the other posts in this site!