Although stainless steel castings have high corrosion resistance and oxidation resistance, once the surface oil and rust are not cleaned for a long time, it will also damage itself. Therefore, stainless steel castings also need to be cleaned on time, and pickling and passivation are the common cleaning methods at present. But how does it actually start cleaning? Let's read the cleaning steps for everyone.

1、 Pretreatment before pickling and passivation:

1. Pickling and passivation pretreatment can be carried out for the spare parts of stainless steel castings after production and manufacturing according to the standard of finishing process card, and the specified items are inspected to meet the standard.

2. For the equipment with repair welding, the welding seam, welding slag and spatter on both sides shall be cleaned. Sand blasting or shot blasting shall be conducted on the surface of the equipment (see the attached equipment process card for details) to remove oil stains and other dirt.

3. When cleaning the foreign matters on both sides of the weld, stainless steel wire brush, stainless steel shovel or grinding wheel shall be used for cleaning. At the end of cleaning, the content of chloride ion in water shall not exceed 25mg / L.

2、 Acid pickling and passivation operation method:

1. Only parts that have been pretreated can be cleaned by pickling and passivation.

2. Pickling solution pickling is mainly used for the overall cleaning of small and unprocessed parts, which can be immersed or painted. When the solution temperature is between 21-60 ℃, check once every 10 minutes until the uniform white etching smoothness is shown.

3. Passivation solution is mainly used for cleaning small glass containers or parts as a whole. Immersion or brushing method can be used. When the solution temperature is 48-60 ℃, it should be checked every 8 minutes. When the solution temperature is 21-47 ℃, it should be checked every 20 minutes until a balanced passivation film is formed on the surface.

4. The surface of acid pickling and passivation parts should be washed with clean water, and any part of the washed surface should be tested with acid litmus test paper to make the pH value between 6.5 and 7.5, and then dry or air dry with compressed gas.

5. Glass containers and spare parts after acid pickling and passivation shall not be bumped and scratched during hoisting and storage.

The surface layer of stainless steel castings will remain various kinds of oil stains, rust, oxide scale, welding spot and other dirt. After acid pickling and passivation, the surface layer will become silver white evenly, which can also improve the corrosion resistance of stainless steel. However, when carrying out cleaning, it is also necessary to be cautious about the operation methods, such as wearing acid resistant clothes, gloves, protective masks, safety goggles and other safety protection methods to prevent injury after contact.