Lead and Its Alloys

In general, lead has a very good resistance to corrosion in a number of environments including atmospheric, aqueous, and other chemical environments. Atmospheric corrosion poses almost no threat to lead due to its excellent resistance to corrosion in most types of atmospheric environments including those containing industrial pollutants (e.g. SO2, SO3, CO2, H2S, etc.). Lead’s inherent corrosion resistance is mostly due to the protective film on its surface, which can form in a wide variety of environments including those containing oxides, sulfates, carbonates, and chromates. An added benefit of this film is that it is insoluble in the corrosive medium in which it is formed, which consequently results in long-term protection in that environment.

Lead is generally resistant to corrosion in fresh water and seawater, except in those water environments containing dissolved oxygen. In soil, lead also typically has a good resistance to corrosion. The presence of organic acids in the soil from wood, usually results in an increased rate of attack. Acetic, nitric and formic acids attack lead readily, but it has a good resistance to sulfuric, sulfurous, chromic and phosphoric acids and adequate resistance to hydrochloric and hydrofluoric acids. The presence of oxygen in acidic and soft water environments causes a significant increase in the corrosion rate. In the presence of most alkaline environments, lead only has a fair resistance to corrosion. Table 47 lists a number of corrosive media and lead’s corresponding resistance to corrosion.

Lead is a very ductile metal with low strength and hardness properties, and due to its softness, it is especially susceptible to erosion corrosion. The corrosion resistance of lead does not vary much between the pure form and its alloys. Therefore, alloys are commonly chosen over pure lead based solely on strength properties. For instance, lead with 3-18% antimony has twice the strength of pure lead, but the strength does decrease rapidly with temperature.