1. Copper sulfate solution method

Periodically immerse the cleaned metal in an acidic copper sulfate solution composed of 50g/LCuS04 solution and 20g/LH2So4 for about 1 minute, then take it out and wash it with water and observe. If the copper film on the metal surface is dense and uniform, it is judged that the metal is clean. If the copper film is not uniform and the adhesion strength is poor, the metal surface is not clean. At this time, the liquid can be refilled at a ratio of 1-2%. Because this method is simple and feasible, it is a simple method suitable for factory use

2. PH value method

Periodically check the pH value of the cleaning solution. According to the process, the pH value of the bath solution is proportioned. The bath solution cannot be completely cleaned within the cleaning time specified in the process. It is necessary to extend the cleaning time and then check the pH value. The fluid can be refilled between the two pH values, and the fluid can be changed or refilled below the second value

3. Water drop method

Under the condition of a certain volume of water droplets on the surface, the larger the diameter of the water droplets spread out on the surface, the smaller the contact angle and the higher the cleanliness. Therefore, the size and shape of the diameter formed on the surface can be used as a basis for a relatively clean degree. It is the shape of water droplets when there is uneven residual dirt on the surface, the middle water remains round and the diameter is quite large.

4. Water film method

Under the condition of a certain volume of water droplets on the surface, the larger the diameter of the water droplets spread out on the surface, the smaller the contact angle and the higher the cleanliness. Therefore, the size and shape of the diameter formed on the surface can be used as a basis for a relatively clean degree. It is the shape of water droplets when there is uneven residual dirt on the surface, the middle water remains round and the diameter is quite large.

5. Spray method

Use a sprayer to spray uniform particulate water droplets onto the cleaned dry surface, and judge its cleanliness by the formation of water droplets. When the surface is very clean, the particulate water droplets will evenly wet the layer on the surface, and the peripheral shape of the condensed water film will be a regular circle after drying.

6. Exhalation method

Blow air on the surface of the dry cleaning object. When water vapor condenses on the surface, a turbid fog will be formed. When the surface is clean, the fog spots are uniform, and when the surface is not clean, the fog spots are uniform. When the surface is very smooth and clean, the fog spots will disappear in a short time.

7. Visual observation method

Observe the grease, rust and other dirt on the surface by direct observation with a magnifying glass, inspection tube and other instruments. It is also possible to use the intensity of the reflected light directly on the surface of the object to understand the pollution. Standards should be set for samples of different cleanliness in advance, and then the samples to be tested can be compared with known samples. The advantage of this method is that the determination speed is fast and the sample does not need to be destroyed. But the experimenter is required to have certain experience. This method is more effective in measuring granular dirt, but has poor accuracy in judging thin film dirt formed by organic matter. In the equipment used, the light source must have a certain light intensity to produce strong reflected and scattered light.