Editing Rust (section)

== Economic effect ==
{{anchor|Economic effect}}
{{Main|Corrosion}}

[[File:Rust wedge.jpg|thumb|upright=.6|Outdoor ''Rust Wedge'' at the [[Exploratorium]] showing the expansion of rusting iron]]
Rust is associated with the degradation of iron-based tools and structures. As rust has a much higher volume than the originating mass of iron, its buildup can also cause failure by forcing apart adjacent parts — a phenomenon sometimes known as "rust packing". It was the cause of the collapse of the [[Mianus river bridge]] in 1983, when the bearings rusted internally and pushed one corner of the road slab off its support.

Rust was an important factor in the [[Silver Bridge]] disaster of 1967 in [[West Virginia]], when a steel [[suspension bridge]] collapsed in less than a minute, killing 46 drivers and passengers on the bridge at the time. The [[Kinzua Bridge]] in [[Pennsylvania]] was blown down by a [[tornado]] in 2003, largely because the central base bolts holding the structure to the ground had rusted away, leaving the bridge anchored by gravity alone.

[[Reinforced concrete]] is also vulnerable to rust damage. Internal pressure caused by expanding corrosion of concrete-covered steel and iron can cause the concrete to [[spall]], creating severe structural problems. It is one of the most common failure modes of reinforced concrete [[bridge]]s and buildings.

<gallery class="center" mode="packed" caption="Structural failures caused by rust">
File:Silver Bridge collapsed, Ohio side.jpg|The collapsed [[Silver Bridge]], as seen from the [[Ohio]] side
File:Collapsed Kinzua Bridge.jpg|The [[Kinzua Bridge]] after it collapsed
File:Nandu River Iron Bridge corrosion - 03.jpg|Rusted and [[Pitting corrosion|pitted]] struts of the 70-year-old [[Nandu River Iron Bridge]]
File:Qew bruecke nf beton kaputt 23 von 46.jpg|Rusting [[rebar]] has expanded and [[spall]]ed concrete off the surface of this [[reinforced concrete]] support.
</gallery>