Galvanized nails

In this activity, galvanized nails are used as a source of zinc. Galvanization is a process by which metals such as steel are dipped in zinc to protect them from rusting. One type of nail is dipped in a hot bath of molten zinc to form a protective coating. Zinc is more easily corroded than iron, so it oxidizes rather than the steel. 

The galvanized nail (bottom) is protected from rusting by the sacrificial oxidation of zinc. 

If the principle behind the operation of photocopiers—the attraction of materials to a static charge—is so basic and well understood, why did it take so long to produce a practical photocopier The answer, as with many such innovations, is that the fundamental concept existed long before the materials necessary to implement the idea. Materials science is a discipline all to its own because of the virtually infinite variety of properties that the elements, as well as the substances derived from the elements, can display. Consider, for instance, the variation in the behavior of aluminum and copper (both of which are used in electrical wiring) and steel nails and galvanized nails (both of which are hit on the head). In the next chapter, we lay the differences on the table—the periodic table, that is. 

If galvanized nails, which have been coated with zinc, are placed in a brown solution containing I2, the solution slowly turns colorless. Adding a few drops of bleach to the colorless solution results in a return of the brown color. Explain what makes these changes occur. 

This experiment is intended to support classroom discussions concerning significant figures, the metric system, and unit conversions. The exercise with galvanized nails is optional. In the absence of the nails, this experiment could be combined with Experiment 13 in one lab period. 

Galvanized sheet metal (can be purchased inexpensively in rolls at builders supply stores) Galvanized nails (optional)... 

Balance the following equation for the chemical reaction that forms zinc phosphate (used in dental cements and for making galvanized nails). 

Freshmen at Phillips University perform an experiment in which they dissolve the zinc from a galvanized nail and measure the mass lost by the nail to tell how much of the nail was zinc. Several students performed the experiment in triplicate and pooled their results ... 

Green wood and a number of South American and African hardwoods containing acidic materials should not come into contact with galvanized steel, since certain acidic substances in these woods have a corrosive effect on zinc. Some preservative treatments for wood can have an adverse effect on zinc-coated steel with which it is in contact. Hot dip galvanized nails should not be used for joints that will be exposed in water, regardless of whether the wood is pressure-treated. In such cases, nails of stainless steel are preferable. 

When iron is coated with zinc, it is resistant to the rusting effects of oxygen and is said to be galvanized. Nails, wire, and large sheets of metal are treated this way to increase the life and use of such metals. 

Rust can also be prevented by placing a sacrificial electrode in electrical contact with the iron. The sacrificial elecfrode musf be composed of a metal that is above iron on the activity series. The sacrificial elecfrode oxidizes in place of the iron, protecting the iron from oxidahon. Anofher way to protect iron from rusting is to coat it with a metal above it in the achvity series. Galvanized nails, for example, are coated with a thin layer of zinc. Since zinc is more active than iron, it oxidizes in place of the underlying iron (just like a sacrificial electrode does). The oxide of zinc is not crumbly and remains on the nail as a protective coating. 

A galvanized nail has a thin layer of zinc on its surface. The zinc oxidizes instead of the underlying iron, forming a tough zinc oxide film that protects the iron. 

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