iron是可数名词吗

　　A boy came towards them, rolling an iron hoop.

　　一个男孩滚着一个铁环朝他们走来。

　　Iron reacts with water and air to produce rust.

　　铁和水及空气发生反应产生铁锈。

　　I'll need to iron that dress before I can wear it.

　　我得先把那件连衣裙烫平再穿。