Stainless steel will appear black scale during processing. In order to improve the appearance and corrosion resistance of stainless steel, the processed stainless steel must be pickled and passivated. The oxide scale generated after welding and high-temperature processing is removed, so that the silver is bright and bright, and the surface of the treated surface is formed into an oxide film mainly composed of chromium, which does not cause secondary oxidation, thereby achieving the purpose of passivation. In order to improve the surface anti-corrosion quality of stainless steel products and prolong their service life.
Pickling can remove the oxide layer on the surface of the workpiece. Passivation is to form a new layer of chromium-rich protective layer on the surface of the workpiece. If it is not treated after pickling, it is more likely to rust. After passivation, the oxidation resistance can be greatly improved.
The anti-corrosion function of stainless steel is mainly due to the surface covered with a very thin (about 1 nm) dense passivation film, which can isolate corrosive substances and is the basic barrier for stainless steel protection. The passivation of stainless steel has dynamic characteristics and should not be regarded as a complete stop of corrosion. Instead, it forms a barrier layer for diffusion, which greatly reduces the reaction speed of the anode. It usually tends to destroy the membrane in the presence of a reducing agent (such as chloride ion), while in the oxidant. The film can be maintained or repaired in the presence of air (such as air).It guarantees the formation of high-quality passivation, because the surface of the stainless steel has an average surface thickness of 10μm by pickling, and the chemical activity of the acid solution makes the dissolution rate of the defect part higher than other parts on the surface, so pickling can The entire surface tends to be evenly balanced, and some of the hidden dangers that were previously prone to corrosion are removed.
xx通过酸洗钝化，铁和氧化铁比铬和铬氧化物优先溶解，并且去除贫铬层，导致铬浓缩在不锈钢表面上。富铬钝化膜的电位高达+1。0V（SCE），接近贵金属的电位，提高了耐腐蚀性的稳定性。不同的钝化处理也会影响薄膜的成分和结构，从而影响生锈。例如，通过电化学改性，钝化膜可以具有多层结构，在阻挡层中形成CrO 3或Cr 2 O 3，或形成玻璃态。氧化膜允许不锈钢最大化耐腐蚀性