What are the common methods of cleanliness testing equipment testing?

1. Visual method

Wet the degreased workpiece surface with water, and arrange the cleanliness according to the complete adhesion of the surface water film. This is the most common method for degreasing quality of aluminum die casting auto parts.

2. Wipe method

Use a clean white silk cloth or filter paper to wipe the surface of the degreasing, cleaned and dried workpiece. If there is no oil stain on the surface of the filter paper or silk cloth, it means that the degreasing effect is good.

3. Copper sulfate method

This method is divided into copper sulfate dipping method and copper sulfate drip method.

①The copper sulfate dipping method is to immerse the degreasing workpiece in an acidic copper sulfate aqueous solution, remove the workpiece from the solution after 1min, and rinse it with water. According to the evaluation of the cleanliness of the copper film, the copper film is complete and uniform, with good gloss and adhesion, indicating that the surface of the workpiece is free of oil stains. This method is suitable for small workpieces.

②The copper sulfate spotting method is to drop the copper sulfate mixed droplets on a representative position (above 10 points) on the surface of the workpiece after degreasing. If the droplets appear pink metal copper spots within 5s, it indicates that the droplets are free of oil stains; If the droplets do not change within 5s, it indicates that there is oil pollution at the droplet position; the longer the waiting time for pink metal copper spots to appear, the heavier the oil pollution is. This method is especially suitable for large workpieces.

4. Oil test paper method

This method is improved on the basis of visual inspection. Drop a polar solution on the surface of the metal workpiece which has been degreasing and rinsed with clean water, spread the solution with a glass rod, and then stick the oil test paper on the solution film. If the oil stains on the surface are removed cleanly, the surface of the oil test paper can be completely in contact with the polar solution on the surface of the metal workpiece, and it will show continuous red; Wet and bead-like, therefore, the color of the oil test paper is sparse dots or blocks. The method has high sensitivity, convenient and quick operation, and is suitable for the detection of oil cleanliness on the surface of metal tools such as steel, copper, and aluminum. GB/T13312-1991 has taken this method as the test basis for the degree of degreasing of steel parts before painting.

5. automotive component instrument free energy test method

This method takes the surface tension of water (72×10-5N/cm) as a typical cleanliness, and then tests the cleanliness of a surface relative to this cleanliness. There are 11 kinds of standard solutions, and their surface tension is about (25~100)×10-5N/cm, and they are listed in the table. During the test, drop a standard drop of a certain number on the surface to be tested. If the drop becomes a bead, use the next standard drop to drop. By analogy, until a certain standard liquid can naturally infiltrate the surface, the lowest No. 1 standard liquid that can form beads on the surface of the metal workpiece will know the measurement result of the surface cleanliness.