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Why Must Turntable Bearings Be Pickled? Pickling Process Flow


We usually call the process of soaking metal parts that have been cleaned and degreased in acid solution acid washing during the production process. Bearings also need to be acid washed, so why does a turntable bearing need to be acid washed? There are mainly two purposes for this. One is to remove the oxide scales or burrs on the surface of the metal by acid washing, and the other is to inspect the metal surface defects for burn scars or corrosion. Below, we will introduce the specific operating process of acid washing for turntable bearings.

  

Purpose of acid washing for turntable bearings

  

Surface purification


The surface of the bearing is cleaned by acid washing, such as acid washing before electroplating, acid washing before phosphating, acid washing to remove oxide scales and burrs, etc. Acid washing liquid is used to choose cold acid washing or hot acid washing according to the condition of the metal surface. Cold acid washing is widely used to remove oxide scales on the surface of the cage.

  

Acid washing inspection


Inspect the surface defects of the bearing by acid washing, which is called acid washing inspection or burn corrosion. It belongs to a detection method and is commonly used with nitric acid cold washing. If there are cracks, decarbonization, peeling, burn scars and other defects on the metal surface, they can be revealed by cold acid washing. This acid washing inspection technology is often classified as NDT (non-destructive testing) method abroad. Most factories use this inspection method to detect surface defects.

  

Choose the correct acid washing technology, use suitable acid washing process (including the selection of acid, corrosion inhibitor, process steps, acid washing time, etc.) according to different application purposes, processing requirements, and different raw materials, and be operated and inspected by dedicated acid washing personnel to ensure the acid washing effect and the quality of bearing products.


Technological process of acid washing for turntable bearings

  

Preparations before acid washing


The bearing parts of industrial turntable bearings need to be cleaned and cannot have oil stains, magnetic powder, dust, and other dirt on the surface; serious rust on the surface also needs to be removed and then acid-washed.

  

Process of acid washing

  

  1. Put the bearing in the solution with a metal cleaning agent for soaking. The concentration of the solution should be between 4% and 5%, and the temperature should be controlled between 75~90 ℃. If it is acid washing, the solution can be diluted with cold water. The soaking time should not be less than 1 minute.

  2. During the process, the turntable bearing should be shaken or moved so that it can fully contact the solution, and the solution should be kept clean. The acid washing time should be controlled within 5 minutes.

  3. Rinse the soaked bearing in flowing cold water to cool it down to room temperature.

  

Inspection after acid washing


Inspect the appearance of the bearing, and its surface should present a consistent silver-gray or light-gray color. Generally, burn scars will be black or bright white, soft spots are dark gray or black, and decarbonization positions are gray-white. During the inspection, the surface of the bearing should not be wiped. If there is any doubt, degreased cotton can be dipped in ethanol or rust inhibitor to wipe it. After the inspection is completed, the bearing should be sent to the anti-rust process in time to avoid surface oxidation and rust again.