技術(shù)交流

4.2化學(xué)去除方法

Methods of chemical removal

化學(xué)去除有不同的選擇，每種方法將在下面進(jìn)行描述。

這些選項可以單獨使用，也可以在必要時相互組合使用。

There are different options available for chemical removal, each of which will be described below.

These options can be used separately or, where necessary, in combination with one another.

4.2.1化學(xué)酸洗

Chemical pickling

  酸洗是一種對不銹鋼表面的強化化學(xué)處理方法，為專業(yè)公司持有。這種方法的優(yōu)點之一是，它可以溶解更小規(guī)模的無機雜質(zhì)，并系統(tǒng)地將它們清除出表面。通常，所有酸洗劑在清洗過程中都會造成少量的材料損失（從1到3μm）。用于此目的的化學(xué)品通?；谒芤褐械臍浞岷拖跛?，并可以浸泡、糊狀和噴霧的形式使用。這些酸的反應(yīng)主要分為以下兩個階段：

?（1）金屬氧化，和

?（2）金屬氧化物的溶解/反應(yīng)形成一種典型的金屬氟化物鹽 

    Pickling is an in intensive chemical treatment of stainless steel surfaces that is reserved for specialist companies. One of the benefits of this method is that it can dissolve even smaller-scale inorganic impurities and systematically clean them off of surfaces. As a rule, all pickling agents cause a minimum amount of material abrasion (from 1 to 3 μm) during the cleaning process. The chemicals used for this purpose are typically based on hydrofluoric acid and nitric acid in aqueous solution, and are available in the form of baths, pastes and sprays. The acids essentially react in the following two-stage process:

? (1) Metal oxidation, and

? (2) Dissolution of the metal oxide / reaction forming metal fluoride as a typical metallic salt

在進(jìn)行酸洗工藝之前，必須去除覆蓋表面的任何東西（例如，標(biāo)簽粘合劑），來確保處理用化學(xué)品能在沒有任何阻礙的同時地接觸表面。

    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.

根據(jù)于各種不同的標(biāo)準(zhǔn)，選擇合適的酸洗劑和合適的酸洗方法，以及正確的參數(shù)：

?要被酸洗的是哪種類型的不銹鋼或哪種等級的合金？

?要移除的薄層范圍？

?被酸洗的部件應(yīng)符合哪些表面要求（例如，根據(jù)DIN EN 4288的最終粗糙度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?

  根據(jù)所用的酸洗劑選擇酸洗參數(shù)，在酸洗、活化和漂洗后，不銹鋼表面將具有一個完全可鈍化的表面。對于自發(fā)形成保護(hù)性鈍化層，隨后建議采用適當(dāng)?shù)幕瘜W(xué)鈍化步驟，之后應(yīng)用符合DIN EN 285（給水）規(guī)范的水沖洗表面，以達(dá)到最終無酸(pH為7)狀態(tài)?？梢灶A(yù)期的被動層通常展現(xiàn)出的平均厚度約為1–3nm。氧化介質(zhì)（如硝酸或過氧化氫）是有效的鈍化劑。

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.

濕化學(xué)鈍化反應(yīng)在幾秒鐘到幾分鐘內(nèi)發(fā)生。

The wet-chemical passivation takes place within a span of a few seconds to a few minutes.

  合適的絡(luò)合劑(NTA、EDTA、GLDA、檸檬酸)，通常用作濕化學(xué) 鈍化溶液中的添加劑，也可用于后處理，以去除存在于表面的任何鐵離子。然而，這些物質(zhì)對不銹鋼表面沒有再鈍化作用，在酸洗后這些加入到硝酸水溶液，實現(xiàn)了相應(yīng)綜合的鈍化作用和最終清洗效果。

    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.

  如果化學(xué)產(chǎn)品用于酸洗、活化、鈍化和事先脫脂，則應(yīng)遵守每個產(chǎn)品的制造商提供的安全數(shù)據(jù)表和處理信息。

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.

  酸洗所涉及的復(fù)雜過程強調(diào)了這類工作需要必須由專家來完成的重要性。這需要確保防止對設(shè)備及其表面的永久性損壞（例如，所謂的“過度酸洗”）。

    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').

4.2.2化學(xué)除銹

Chemical derouging

  在主要使用有機絡(luò)合劑溶液的化學(xué)除銹中，位于不銹鋼表面或粘附在不銹鋼表面的薄膜如重金屬氧化物顆粒（鐵、鉻、鎳等）被清洗掉，不會留下任何殘留物，也不會侵襲或損壞不銹鋼表面。在復(fù)雜的部件的幾何情況下這是一個重要的，往往比化學(xué)酸洗具有優(yōu)勢的決定性工藝，這意味著化學(xué)除銹工藝提供更大的可靠性。

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.

  化學(xué)處理在一個封閉的腔室中進(jìn)行，通過可控地潤濕腔室的內(nèi)表面，清潔溶液保持在可控的溫度下。原則上，也可以用適當(dāng)?shù)那逑匆和耆畛渫耆芊獾那皇?，并在預(yù)定的應(yīng)用時間內(nèi)執(zhí)行清洗程序。作為一種替代方法，通過將溶液通過適當(dāng)?shù)谋煤?/span>腔體范圍內(nèi)噴淋頭循環(huán)，也可以使用相對少量的流體成功地進(jìn)行有效的清洗。

    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.

  依據(jù)實際清潔步驟(=去銹程序)之后,使用特定的鈍化溶液再鈍化受影響的腔室表面,然后用符合DIN EN 285(給水)規(guī)格的水沖洗以去除所有殘留的酸液。最后一步后,使用電導(dǎo)儀測量來檢查酸去除的效果。

    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.

  通過選擇化學(xué)和環(huán)境更溫和的除銹溶液，這種純粹的化學(xué)處理——不像化學(xué)酸洗——消除了表面侵蝕和表面粗糙度的惡化，即使更長的使用時間，因為所涉及的不銹鋼合金在除銹溶液中的化學(xué)耐腐蝕性能沒有降低。

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.

來自：德國的錢伯斯工作組(德語縮寫：AKK)的手冊