rusting grade

例句：

1. 1. The rusting gradeof the metal is a critical factor inits durability.
   金属的锈蚀等级是其耐久性的关键因素。
2. 2. The rusting grade of the old car has increasedsignificantly over the years.
   这辆旧车的车漆锈蚀等级在这些年里显著增加。
3. 3. The rusting grade of thebridge was determined by an expert engineer.
   桥梁的锈蚀等级是由一位专家工程师确定的。