生锈

例句：

1. 1. The metal object has been exposed to the elements for too long and is now rusting.
   这个金属物体暴露在元素中太久了，现在开始生锈。
2. 2. The car's engine was rusted due to neglect.
   由于忽视，这辆车的引擎已经生锈了。
3. 3. The old iron gate is starting to rust, which is a sign of age.
   旧铁门开始生锈，这是老化的迹象。