| 锻造与铸造不锈钢对钝化工艺的影响 |
| 添加时间：2018/10/31 15:02:46 浏览次数： |
| 不锈钢材料机加工后的钝化工艺是制药设备与工程领域非常关键的质量控制点，钝化是指使金属表面转化为不易被氧化的状态而延缓金属腐蚀速度的方法。钝化的效果，包括钝化深度和表面金属元素的优化分布（如铬铁比），将决定金属钝化后的抗腐蚀性和腐蚀速率。钝化是洁净表面有氧气存在时的自发现象，可在不锈钢表面生成钝化膜。通过化学处理，不锈钢表面钝化膜可一定程度增强。钝化的一个先决条件是对表面的清洗程序。所述的清洗程序应包含所有必要的表面污物的清除（油脂、颗粒等）以保证锻件表面最佳的抗腐蚀性能、保护产品不被污染的性能和合金表面外观的达标。最终化学钝化处理的目的是确保合金表面无铁元素及其他污物存在以实现最佳的抗腐蚀状态。 Passivation process of stainless steel after machining is a very important quality control point in pharmaceutical equipment and engineering field. Passivation is a method to slow down the corrosion of metal by transforming metal surface into a state that is not easy to be oxidized. The effect of passivation, including the depth of passivation and the optimal distribution of metal elements on the surface (such as the ratio of ferrochrome to chromium), will determine the corrosion resistance and corrosion rate of passivated metals. Passivation is a spontaneous phenomenon on the surface of clean surface when oxygen exists, and passivation film can be formed on the surface of stainless steel. By chemical treatment, the passivation film on the stainless steel surface can be enhanced to a certain extent. A prerequisite for passivation is the cleaning procedure for the surface. The cleaning procedure shall include all necessary surface contamination removal (grease, particles, etc.) to ensure the best corrosion resistance of the forging surface, to protect the product from contamination, and to meet the requirements of the alloy surface appearance. The ultimate goal of chemical passivation is to ensure that the alloy surface is free of iron and other contaminants to achieve the best corrosion resistance. 钝化分为自发性钝化、化学钝化和电化学钝化。在不锈钢表面生成钝化膜，是不锈钢洁净表面有氧气存在时的自发现象，成为自发性钝化。通过化学和电化学处理，可实现不锈钢表面钝化膜一定程度的增强。某些钝化剂（化学药品）所引起的金属钝化现象，称为化学钝化，如浓HNO3、浓H2SO4、HClO3、K2Cr2O7、KMnO4等氧化剂都可使金属钝化。金属钝化后，其电极电势向正方向移动，使其失去了原有的特性，如钝化了的铁在铜盐中不能将铜置换出，又比如Fe→Fe2+电位为-0.44V，钝化后跃变为+0.5-1V。此外，用电化学方法也可使金属钝化，如将Fe置于H2SO4溶液中作为阳极，用外加电流使阳极极化，采用一定仪器使铁的电位升高一定程度，Fe就钝化了，由阳极极化引起的金属钝化现象，叫阳极钝化或电化学钝化。 Passivation is divided into spontaneous passivation, chemical passivation and electrochemical passivation. The formation of passivation film on the surface of stainless steel is a spontaneous phenomenon in the presence of oxygen on the clean surface of stainless steel. The passivation film on stainless steel can be enhanced to some extent by chemical and electrochemical treatment. Some passivators (chemicals) caused by the metal passivation phenomenon, known as chemical passivation, such as HNO3, H2SO4, HClO3, K2Cr2O7, KMnO4 and other oxidants can passivate the metal. After passivation, the electrode potential moves in the positive direction, so that it loses its original characteristics, such as passivated iron can not replace copper in copper salt, such as Fe Fe2 + potential of - 0.44V, passivation jump to + 0.5 - 1V. In addition, electrochemical methods can also passivate the metal, such as putting Fe in H2SO4 solution as an anode, polarizing the anode with an external current, using a certain instrument to raise the potential of iron to a certain extent, Fe passivation, caused by anodic polarization of metal passivation phenomenon, called anodic passivation or electrochemical passivation. 电化学钝化是阳极极化时，金属的电位发生变化而在电极表面上形成金属氧化物或盐类。这些物质紧密地覆盖在锻件表面上成为钝化膜而导致金属钝化，化学钝化则是像浓HNO3等氧化剂直接对金属的作用而在表面形成氧化膜。化学钝化时，加入的氧化剂浓度还不应小于某一临界值，否则不仅无法导致钝态，反而还会引起金属更快的溶解。 Electrochemical passivation is an anodic polarization in which metal potential changes and metal oxides or salts are formed on the electrode surface. These substances are tightly coated on the surface of the forgings to form passive films, which lead to metal passivation. Chemical passivation is the formation of oxide films on the surface of the forgings by the direct action of oxidants such as HNO3. In chemical passivation, the addition of oxidant concentration should not be less than a certain critical value, otherwise not only can not lead to passivation, but also lead to faster dissolution of metals. 硝酸的化学性质随浓度变化而变化，稀硝酸主要体现的是其强酸性，浓硝酸主要体现其强氧化性。而浓硝酸接触到不锈钢表面，则会氧化金属，并生成致密的氧化层，附着于表面形成钝化层。 The chemical properties of nitric acid change with the concentration, dilute nitric acid mainly reflects its strong acidity, concentrated nitric acid mainly reflects its strong oxidation. When concentrated nitric acid touches the surface of stainless steel, it oxidizes the metal and forms a dense oxide layer which adheres to the surface to form a passivation layer. |
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