Corrosion Resistance in Various Environments

Zinc has a good resistance to all types of atmospheres, but moist and acidic environments can be problematic for zinc in terms of corrosion. Weak and strong acids and strong bases tend to attack zinc more readily, but it is generally resistant to weak bases. Industrial environments can be corrosive to zinc, especially if the contain sulfur dioxides. Zinc is susceptible to corrosion by sulfur dioxide, chlorides, and low-grade glycerin, but it is resistant to dry chlorine and hydrogen sulfide.

The corrosion rate of zinc is dependent on temperature, pH, and oxygen concentration. There seems to be a strong relationship between corrosion and oxygen content, as it increases with increasing oxygen content in the environment. Zinc is corroded 8 times faster in water with oxygen gas present than in water with no gases. In oxygen deficient environments, pitting tends to occur, while oxygen abundant environments lead to more uniform corrosion. The corrosion rate of zinc is temperature dependent, and it increases rapidly from room temperature to about 60°C, then decreases significantly at 100°C.

Zinc is susceptible to environments containing organic vapors, which tend to attack the metal’s surface. Organic substances therefore, may be very corrosive to zinc, if they produce organic vapors or other products such as sulfur or halogen compounds. Zinc does tend to be resistant, however, to anhydrous organic liquids with a neutral pH.

Zinc has a good resistance to water, but it is more susceptible to corrosion if oxygen or carbon dioxide is present, or if the water is at an elevated temperature, or if the water is strongly aerated or agitated. Furthermore, soft water attacks zinc more readily than hard water, and steam can also be damaging, if zinc is exposed to it in a continuous manner.