Reading Selection, Lesson 24
The Work Never Ends
The Golden Gate Bridge is one of the world's great bridges. It spans 2.7 kilometers across the Golden Gate Strait at the end of San Francisco Bay. More than 1.5 billion cars have crossed over it. It contains 75 million kilograms of steel. It can withstand powerful tides, hurricane winds, and major earthquakes. But one thing could send it tumbling into the bay below: corrosion. The iron in steel combines with the oxygen in air to form iron oxide, or rust. Water and salt, which the bridge is constantly exposed to, greatly speed up rust formation. To keep the mighty bridge from crumbling apart, maintenance crews must constantly battle rust.
Applying the Paint
A painter puts down a primer coat. Primer sticks to the metal, but it isn't that tough or waterproof. So after the primer dries, the painter puts on two protective top coats of paint that keep out air and water.
How do car or bicycle manufacturers stop or reduce rusting? Draw a simple sketch of either a car or a bike and label all the different methods of rust prevention you can identify.