Foundation, Concrete and Earthquake Engineering

How Zinc Protects Metals And How It Is Applied

Zinc plating prevents decay of the metal by forming a physical barrier on metal and by acting as a barrier if this barrier is damaged. Zinc coatings provide the most effective way of protecting steel against corrosion. Zinc reacts with oxygen to form zinc oxide that further reacts with water molecules in the air to form zinc hydroxide. Finally zinc hydroxide reacts with carbon dioxide in the atmosphere to yield a thin, impermeable, firm and quite insoluble dull grey layer of zinc carbonate which protects it from further corrosion.

How Zinc Protects

When left unprotected, steel will decay in almost any environment. Zinc coatings stop corrosion by providing two protections,namely a physical barrier and cathodic action.

Barrier Protection

Zinc coatings provide a continuous, impervious metallic barrier that does not allow moisture to contact steel. Without direct moisture contact, there is no corrosion.

Cathodic Protection

Another outstanding protection is zinc’s remarkable ability to galvanic ally protect steel. When bare steel is exposed to moisture, such as at a cut edge or surface scratch, steel is protected by the sacrificial loss of zinc in the surroundings of the exposed steel. In the immediate presence of zinc, steel will not corrode until all the zinc has been sacrificed. This is particularly important for coated steel sheet since corrosion will continually undercut both aluminum or paint barrier coatings. The presence of zinc is the key to cathodic protection.

The bond between the zinc and steel is metallurgical so that a coil of zinc coated steel can be cut, punched and formed without damaging the zinc coating.

Zinc Plated Metals

Zinc Plated metal is often used in the construction of warships, such as carriers and submarines. The water and salt repellent qualities of the steel with its solid zinc coating make it the ideal material to use for hulls. It is also used for building structures that will remain strong for many decades. Zinc Plated steel is an ideal material for a multitude of building applications. In the residential construction market, Zinc plated steel has particular and cost-effective applications in framing, roofing, and rain ware, heating or cooling and venting and household appliances.
How Zinc are Applied

There are two processes namely hot dip and electro galvanized to apply Zinc. Hot dip plating put a thick robust layer that is necessary for the protection of the underlying metal. This is the case in automobile bodies, where additional rust proofing paint will be applied. The protection of steel from corrosion by the hot dip zinc galvanizing has been practiced for almost 200 years, and the technique is still unequaled for the long term protection.

A thinner form of plating is applied by electroplating, called "electro galvanization". However, the protection this process provides is insufficient for products that will be constantly exposed to acidic materials such as salt water. Most nails made today are electro-galvanized.

Galvanized metal has made it possible for humanity to enjoy long lasting shelters, as well as explore the ocean and the ocean floor in perfect safety. For over a century, zinc has enhanced the longevity and performance of steel. There is no doubt that humankind will continue to find ways to utilize this valuable construction tool in new and exciting ways in the years to come.

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