The metal has corroded (away) because of rust.

金属因为生锈不停地被腐蚀。

These remarkable hills owe their peculiar shapes to the mildly acid waters of the Li River, whose meandering course over eons of time has corroded away their basis, until only the rocky course remained.

这些神奇的山地的嶙峋奇秀归功于漓江那弱酸性的水质，亿万年曲折线路已经侵蚀掉它们的主要部分，直到只剩下坚硬的河道。