钝化是指材料变得“钝化”的过程,这意味着它受腐蚀等环境因素的影响较小。它涉及自发形成一层非常薄的非反应性表面。 电影 它起到屏障作用,保护主体材料免受进一步侵蚀。这种薄膜通常是几纳米厚的氧化物或氮化物层。

(图片仅供参考)
钝化是指材料变得“钝化”的过程,这意味着它受腐蚀等环境因素的影响较小。它涉及自发形成一层非常薄的非反应性表面。 电影 它起到屏障作用,保护主体材料免受进一步侵蚀。这种薄膜通常是几纳米厚的氧化物或氮化物层。
钝化的机制是电化学的。当铬、铝或 钛 当金属暴露于氧化环境(例如空气或某些酸)时,其表面会迅速氧化。如果生成的金属氧化物稳定、致密、无孔且牢固地附着在金属表面,则会形成一层保护性钝化层。这层钝化层非常薄,通常只有1-3纳米,但它足以通过阻止金属与腐蚀环境直接接触来显著减缓腐蚀速度。
The stability of this passive film is dependent on the environment, particularly pH and the presence of certain ions like chlorides. For example, the chromium oxide ([latex]Cr_2O_3[/latex]) layer on stainless steel is highly effective in many environments but can be locally broken down by chloride ions, leading to 点蚀. The breakdown and reformation of this passive layer is a dynamic process. If the film is mechanically scratched or damaged, the exposed metal will often repassivate almost instantly, a property known as self-healing.
Passivation can be a natural process or can be enhanced artificially through chemical treatments, such as dipping stainless steel in nitric or citric acid to remove free iron from the surface and encourage the formation of a more robust chromium-rich oxide layer. This process is distinct from applying a coating, as the passive layer is formed from the base metal itself.
钝化
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