酸洗是一种金属表面处理方法，用于除去污渍、锈等。

酸洗主要使用盐酸或硫酸。盐酸虽然比硫酸贵，但它速度快，同时金属损耗小。碳素钢通常用盐酸或硫酸酸洗。合金钢常用磷酸，硝酸或氢氟酸。耐酸性强的铬镍钢需要用盐酸和硝酸酸洗。大多数铜合金用稀硫酸，但黄铜用浓硫酸、硝酸与氯化钠和煤烟的混合液酸洗。钢板酸洗后，若暴露于高湿度的环境下，会氧化生锈。因此，要涂一层油膜或防水涂料。此油膜必须在电镀或涂漆前去除。

Pickling is a metal surface treatment used to remove impurities, such as stains, inorganic contaminants, rust or scale from ferrous metals, copper, precious metals and aluminum alloys. A solution called pickle liquor, which contains strong acids, is used to remove the surface impurities. It is commonly used to descale or clean steel in various steelmaking processes.