某些合金元素含量较高的镍铬不锈钢在经过热处理后,其表面上生成一种含有镍铬等合金元素氧化物的氧化皮。这种氧化皮具有致密的结构,特别是靠近钢基体的一层中,有时几乎完全由铬或镍的氧化物组成。含有铬及镍的氧化皮极难溶于硫酸或盐酸溶液中,而且致密的氧化皮使酸溶液很难渗过它而与金属接触。因此,这类合金钢经常不能用单一的硫酸或盐酸溶液来酸洗,需要使用活性较强的化学溶液。为了酸洗镍铬含量较高的不锈钢,通常采用由硫酸、硝酸、盐酸、氢氟酸以及它们的一些盐类按各种不同比例配成的水溶液。由于利用酸洗来去除不锈钢钢管表面的氧化皮是一项非常细致的工作。操作稍一不慎,就会使酸洗过的表面出现各种缺陷或由于氧化皮、残渣等去除得不干净 Some nickel-chromium stainless steel with a higher content of alloying elements generates a scale containing oxide of alloying elements such as nickel-chromium on its surface after heat treatment. This scale has a dense structure, especially in a layer close to the steel substrate, sometimes almost entirely composed of chromium or nickel oxides. Oxide scale containing chromium and nickel is extremely difficult to dissolve in sulfuric acid or hydrochloric acid solution, and the dense scale makes the acid solution difficult to penetrate it to contact with the metal. Therefore, such alloy steels often can not be pickled with a single sulfuric acid or hydrochloric acid solution and require the use of more aggressive chemical solutions. For pickling of stainless steels with high Ni-Cr contents, aqueous solutions of sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid and some of their salts in various proportions are usually used. Since the use of pickling to remove the surface of stainless steel pipe is a very delicate work scale. Slight careless operation, it will pickling the surface of a variety of defects or due to oxide, residue, etc. removed unclean