清洗金屬表面

Question

在工業上常用鹽酸來清洗金屬表面。
請問：硫酸或硝酸等的強酸也可清洗金屬表面嗎？
是否有需注意的地方 。

Answer 1

鹽酸是還原酸,可以把鐵鏽Fe2O3還原成FeCl2.業界多用18%的鹽酸來清洗鋼鐵製品.反應如下:Fe2O3 + Fe + 6HCl → 3FeCl2 + 3H2O       FeCl2 溶於水,所以可以去除氧化層.硫酸也可以拿來清潔鋼鐵,但是比較少用,因為速率不如鹽酸,而且清潔後表面比較不亮.但是可用來清潔銅器.見下表:ApplicationFormulationCommentsOxide removal from copper, brass, bronze, nickel silver and other copper alloys containing high percentages of copper.10 to 25% hot sulphuric acid with 5 to 10% potassium dichromate added.Pickling can be done at same time flux is removed. Will work on carbon steels, but if pickle is contaminated with copper, the copper will plate out on the steel and will have to be removed mechanically. This sulphuric pickle will remove copper or cuprous oxide stains from copper alloys. It is an oxidizing pickle, and will discolor the silver filler metal, leaving it a dull gray.Oxide removal from irons and steels.A 50% hydrochloric acid solution, used cold or warm, More diluted acid can be used (10 to 25%) at higher temperatures (140-160°F/60-70°C.)A mixture of 1 part hydrochloric acid to 2 parts water can be used for Monel and other high nickel alloys. Pickling solution should be heated to about 180°F/80°C. Mechanical finishing is necessary for bright finishes. This HCI pickle is not like bright dips on nonferrous metals.硫酸,硝酸以及氫氟酸,多用在不鏽鋼的清洗上,下表是ASTM A380 訂的不鏽鋼去氧化層( Pickling )的流程.Table 2. Pickling procedures. Refer ASTM A380GradeTreatmentTemperatureTimeAll stainless steels except free machining grades. (Useful to loosen heavy scale prior to other treatments)8-11% sulphuric acid65-80°C5-45 minutesGrades with less than 16% Chromium (except free machining grades e.g. 416)15-25% nitric acid + 1-8% hydrofluoric acid20-60°C5-30 minutesFree machining grades and grades with less than 16% Chromium10-15% nitric acid + 0.5-1.5% hydrofluoric acid20-60°C5-30 minutes