Zinc is the 23rd most abundant element in the earth's crust. Sphalerite, zinc sulfide (ZnS; i.e, zinc bland), is and has been the principal ore mineral in the world.

Zinc is necessary to modern living and in tonnage produced, stands fourth among all metals in world production—being exceeded only by iron, aluminum, and copper. Zinc uses range from metal products to rubber and medicines. About 3/4 of zinc used is consumed as metal, mainly as a coating to protect iron and steel from corrosion (galvanized metal), as alloying metal to make bronze and brass, as zinc-based die casting alloy, and as rolled zinc. The remaining 1/4 is consumed as zinc compounds mainly by the rubber, chemical, paint, and agricultural industries. Zinc is also a necessary element for proper growth and development of humans, animals, and plants; it is the second most common trace metal, after iron, naturally found in the human body.

Corrosion of Zinc in Water
Zinc is resistant to corrosion by chemicals over a pH range from 6 to 12.5. It produces white corrosion product when kept wet especially when freshly exposed.

The corrosion of zinc in water is largely controlled by the impurities present in the water. Naturally occurring waters are seldom pure; even rainwater, which is distilled by nature, contains nitrogen (N2), oxygen (O2), carbon dioxide (CO2), and other gases, as well as entrained dust and smoke particles.

Under the ground with eroded soil, water carries decaying vegetation, living microorganisms, dissolved salts, and colloidal and suspended matter. Water that seeps through soil contains dissolved CO2 and becomes acidic (H2 + CO2 ----> H2CO3). Groundwater also contains salts of calcium, magnesium, iron, and manganese. Seawater contains many of these salts in addition to its high NaCl content.

All of these foreign substances in natural waters affect the structure and composition of the resulting films and corrosion products on the surface, which in turn control the corrosion of zinc. In addition to these substances, such factors as pH, time of exposure, temperature, motion, and fluid agitation influence the aqueous corrosion of zinc.

As in the atmosphere, the corrosion resistance of a zinc coating in water depends on its initial ability to form a protective layer by reacting with the environment. In distilled water, which cannot form a protective scale to reduce the access of oxygen to the zinc surface, the attack is more severe than in most types of domestic or river water, which do contain some scale-forming salts.

The scale-forming ability of water depends principally on three factors

• the hydrogen ion concentration (pH value),
• the total calcium content, and
• the total alkalinity.

If the pH value is below that at which the water would be in equilibrium with calcium carbonate (CaCO3), the water will tend to dissolve rather then to deposit scale. Waters with high content of free CO2 also tend to be aggressive toward zinc.