If this is the first time you’re seeing the word corrosion, you will be surprised with how important this term can be for your everyday life! Essentially, corrosion is the deterioration of materials like copper or steel over time. It’s a big problem for engineers and other architects who frequently use metal products in their structures, because corrosion can be a safety hazard! To see what I mean, take a look at the following bridge collapses that occurred due to corrosion.

When the NASCAR Winston stock car race ended, hundreds of pedestrians made their way back to the parking lot by crossing a pedestrian bridge that overlooked U.S. Route 29 in North Carolina. As they were making their way across, the concrete and steel walkway snapped in half, and pedestrians fell to the highway below. The bridge collapse injured 107 people and 13 were in critical condition.

After an inspection, it was determined that all 11 steel cables that were holding the bridge together were corroded, and the bridge bustled under the weight. The corrosion was caused by too much calcium chloride, an inorganic salt compound that’s highly corrosive to steel, mixed into the grout that cemented the bridge’s steel cables in place. The compound is acceptable in small amounts, but the construction company that built the bridge used about 40 times more calcium chloride than what was regulated!

Nearly 50 lawsuits were filed against the speedway and the construction company with settlements of millions of dollars — just to expedite the drying process.

The U.S. Highway 35 bridge, nicknamed the “Silver Bridge” since it was the country’s first aluminum-painted one, was a major transportation route between West Virginia and Ohio. During rush hour traffic, the bridge suddenly collapsed into the Ohio River and 75 vehicles were submerged. The tragedy killed 46 people and seriously injured nine.

The cause of failure was from stress corrosion and corrosion fatigue. Years before the collapse, a tiny crack appeared in a suspension chain on the bridge, and the crack grew bigger as time went on. However, it went unnoticed by bridge inspectors because technology did not allow inspectors to see the crack.

Constructed in the mid 1920s, the steel used for the bridge was not known for being susceptible to corrosion, so disaster was inevitable. In addition, the bridge was designed for Model-T Ford, which had an approximate weight three times less than cars in 1967!

You would never believe it, but this 3,300-ton, half-mile-long railroad bridge in north-central Pennsylvania was once deemed the Eighth Wonder of the World. The bridge collapsed when strong thunderstorms with 80 mph winds came through the region and sent most of the bridge crashing into the gorge below.

Built from iron 1882 and reconstructed using steel in 1900, the bride fell into disrepair and became covered in rust. Its cracked foundation turned orange with age, and its supportive columns became weak and shed rust flakes everywhere. It was deemed such a safety hazard that state officials closed the bridge to train and pedestrian traffic because they feared strong winds could easily topple it.