Before the pickling process can be applied, anything covering the surface (e.g., adhesive labels) must be removed to ensure that the treatment chemicals can reach the surface at the same time without any hindrances.
➡被酸洗的部件应符合哪些表面要求（例如，根据DIN EN 4288的最终粗糙度Ra/Rz）？
Selecting the proper pickling agent and the appropriate pickling method, as well as the correct parameters, depends on various different criteria:
➡ Which type of stainless steel or grade of alloy is being pickled?
➡ How extensive are the films that are to be removed?
➡ Which surface requirements (e.g. final roughness Ra/Rz in accordance with DIN EN 4288) will the pickled component be subject to?
根据所用的酸洗剂选择酸洗参数，在酸洗、活化和漂洗后，不锈钢表面将具有一个完全可钝化的表面。对于自发形成保护性钝化层，随后建议采用适当的化学钝化步骤，之后应用符合DIN EN 285（给水）规范的水冲洗表面，以达到最终无酸(pH为7)状态。可以预期的被动层通常展现出的平均厚度约为1–3nm。氧化介质（如硝酸或过氧化氢）是有效的钝化剂。
Depending on the pickling agent used / pickling parameters selected, the stainless steel surface will have a fully passivatable surface after the pickling, activating and rinsing. For a spontaneous formation of a protective passive layer, a suitable chemical passivation step is subsequently recommended, after which the surface should be rinsed with water that meets the specifications of DIN EN 285 (feed water) to achieve a final acid-free (pH of 7) state. The passive layers that can be expected normally exhibit an average thickness of approx. 1–3 nm. Oxidising media (e.g. nitric acid or hydrogen per0
oxide) are effective passivating agents.
The wet-chemical passivation takes place within a span of a few seconds to a few minutes.
Suitable complexing agents (NTA, EDTA, GLDA, citric acid)—normally used as an additive in wet-chemical passivation solutions—can also be used for post-treatment to remove any iron ions present on the surface. However, these substances do not have a repassivating effect on stainless steel surfaces, though it should be added that when aqueous nitric acid is used in activation after pickling, a corresponding synthesis of passivation effects and final cleaning is achieved.
Where chemical products are used for pickling, activation, passivation and also for degreasing beforehand, the safety data sheets and processing information provided by the manufacturer should be observed for each product.
The complex processes involved in pickling underscore the importance of the need for this type of work to be performed solely by a specialist. This is necessary to ensure that permanent damage to equipment and its surfaces is prevented (e.g. what is referred to as 'overpickling').
In chemical derouging that involves the use of a predominantly organic complexing agent solution, films such as heavy metal oxide particles (of iron, chromium, nickel, etc.) located on or adhering to stainless steel surfaces are chemically cleaned off of the surfaces without leaving behind any residues, and without attacking or damaging the stainless steel surfaces. This is an important and, in the case of complex component geometries, often decisive process advantage over chemical pickling, which means that chemical derouging delivers much greater process reliability.
The chemical treatment takes place in a closed chamber by means of a controlled wetting of the chamber's interior surfaces with cleaning solutions kept at controlled temperatures. In principle, it is also possible to completely fill a fully sealed chamber with a suitable cleaning fluid, and to carry out the cleaning programme over a predetermined application time. As an alternative, an effective cleaning can also be successfully carried out using a relatively small amount of fluid by circulating the solution through suitable pumps and spray heads in the chamber area.
依据实际清洁步骤(=去锈程序)之后,使用特定的钝化溶液再钝化受影响的腔室表面,然后用符合DIN EN 285(给水)规格的水冲洗以去除所有残留的酸液。最后一步后,使用电导仪测量来检查酸去除的效果。
Following the actual cleaning step (=derouging procedure), the affected chamber surfaces are repassivated using special passivation solutions and are then rinsed with water that meets the specifications of DIN EN 285 (feed water) to remove all remaining acid. After this last step, an electrical conductance measurement is used to check the effectiveness of the acid removal.
By choosing derouging solutions that are chemically and environmentally much gentler, this purely chemical treatment—unlike chemical pickling—eliminates surface attacks and deterioration of the surface roughness, even with longer application times, since the chemical resistance of the stainless steel alloys involved is not decreased in the derouging solutions.