Zinc-coated nail

Smith, R. S., Johnson, E. L. and Cserjesi, A. J., Corrosion of Zinc-Coated Nails Used with Preservative-Treated Western Red Cedar Shakes in Service. Document No. IRG/WP/ 3197, International Research Group on Wood Preservation, Stockholm (1982)... 

AGSCO has determined that they stand to lose over a billion dollars if the claim is true. They have come to I.O.N.S. and have asked us to take a look at galvanized steel samples from both the galvanized sheet metal stock purchased by Titanic and also a batch of galvanized roofing nails manufactured at about the same time. They want us to determine the amount of zinc coating on the steel. They would like us to report the results both in percent zinc and also in grams of zinc per cm2 of steel. They want us to measure both the sheet metal and the nails, since if there is a problem with the sheet metal, then there also may be a problem with the nails, since they were manufactured at about the same time. 

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. 

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. 

Over the next couple of days observe the pennies. The nail in contact with the zinc should accumulate much less rust compared to the unprotected nail. The nail not in contact with zinc will show signs of oxidation in just a few hours. Appreciable rust will accumulate on this nail. The zinc oxidizes on the other nail, but the oxidation results in a protective coating of zinc oxide forming on the zinc. 

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. 

Uses Thixotrope for high polarity and oxygenated solv. systems such as nail lacquers, paints/coatings (nitrocellulose lacquers, sol n. vinyls, epoxies, acrylics, wash primers, inorg. zinc-rich primers, chlorinated mb-ber, unsat. polyesters)... 

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. 

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