It's a $6 billion scourge that afflicts Navy destroyers, cruise ships and historic vessels like the Queen Mary without fear or favor.
It's such a problem that professional organizations and conferences are dedicated to its existence -- and its suppression.
It's also on your shower head.
The orange stain of metal corrosion may be a nuisance in the bathroom, but on ships, it can be catastrophic. Hulls can collapse, ballast tanks weaken and motors fail, all because of rust. There's no way to fully eradicate it.
The only option: constant vigilance.
"Ships are full of saltwater systems, they're full of salty ocean air," said Scott Tait, a retired Navy captain who most recently was at the helm of the guided-missile destroyer Zumwalt. "Corrosion through the entire ship is a huge, huge issue."
Humanity has been battling rust since people first began using metal for their own purposes. The Bible talks about it, as do Greek and Roman writings and works by William Shakespeare, said Jonathan Waldman, author of the book "Rust: The Longest War." He describes rust as "the most destructive natural disaster on Earth."
The damage caused by wildfires and earthquakes is immediate and unmistakable. But the wide-ranging deterioration wrought by rust is "far greater," he said, even if it doesn't always make headlines.
Waldman ticks off the toll of corrosion: plane crashes, bridge collapses, countless cars falling apart and a near-accident at a nuclear reactor.
"What rust has done is almost limitless," he said.