Metal Types and Corrosion

Metal Types and Corrosion

The deterioration of a material resulting from a chemical or electro-chemical reaction with its environment is known as corrosion. Corrosion is associated with metals that consist mostly of iron or ferrous alloys.

Certain environments tend to be more corrosive than others and this will affect the rate of corrosion. Likewise, a metal’s physical and chemical properties contribute to the rate at which it will rust, a product of corrosion consisting of various iron and hydrated iron oxides.

What metals are most corrosive? At the heart of why certain metals corrode is energy. The energy difference between metals and their ores can be expressed in electrical terms that are related to formation heats of the compounds. The difficulty of extracting metals from their ores in terms of the energy required, and the resulting tendency to release this energy by corrosion, is reflected by the relative positions of pure metals in a list.

most corrosive metals

Metals in the Order of Energy Required to Convert Oxides to Produce 1 kg of Metal

Metal Oxide Energy (MJ kg-1)
Lithium (Li) Li2O 40.94
Aluminum (Al) Al2O3 29.44
Magnesium (Mg) MgO 23.52
Tellurium (Ti) TiO2 18.66
Chromium (Cr) Cr2O3 10.24
Sodium (Na) Na2O 8.32
Iron (Fe) Fe2O3 6.71
Zinc (Zn) ZnO 4.93
Potassium (K) K2O 4.17
Nickel (Ni) NiO 3.65
Copper (Cu) Cu2O 1.18
Lead (Pb) PbO 0.92
Platinum (Pt) PtO2 0.44
Silver (Ag) Ag2O 0.06
Gold (Au) Au2O3 -0.18

Understanding the nature of a given metal helps to ensure proper materials selection and the engineer’s confidence in the ultimate durability of his/her design. This Materials Performance article further explains why metals corrode and how a metal’s properties affect its oxidation rate or corrosiveness.

engineering materials for corrosion control

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While no material is corrosive-resistant in all situations, materials selection is essential to the prevention of many types of failures. This article from Materials Performance takes a broader look at what goes into selecting the proper metal or material for optimum use in design.

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