Pretreatment - selection of cleaning process

Due to the different material processing technology, the residual oil pollution and other pollutants on the metal surface are different. In order to ensure the cleaning effect, when the requirements are higher, special cleaning agent and cleaning process should be used for treatment. For the collinear treatment of many metal materials, the cleaning process needs to be designed properly, which is very important: it can not only reduce the production cost, but also improve the efficiency and product quality.

At present, most of the oil and pollution removal processes are very casual and backward. It seems that the cost of liquid medicine has been reduced, but the total cost is higher due to the increase of other expenses. The main reasons for the current situation are: the product processing enterprises do not know much about chemical technology; Processing enterprises only consider the chemical unit price, not the total consumption and single product cost; Unwilling to adopt new technology, have inertial thinking and inertia.

So how does a metal processing company choose an excellent pretreatment process?

1. Understand the processing technology and chemical reaction principle of the products to be produced;

2. Understand the processing technology of metal raw material suppliers and the residual oil pollution components;

3. Remove the function of oil equipment;

4, familiar with the application environment and technology of various cleaning agents;

5. Understand the advantages and disadvantages of the process to produce products, and develop better process;

6. Adopt environment-friendly technology and materials to save energy and reduce carbon emission.

Case study:

Peeling and peeling after electroplating

1, the surface of the workpiece is not clean oil treatment caused by coating adhesion decline, serious moisture absorption after peeling.

2, metal parts before plating rust or oxidation, cause coating rough or blistering.

3, poor activation will cause coating adhesion to decline.

4. The passivation layer on the metal surface, which is not easy to remove, causes a serious reduction of adhesion. Such as: sodium nitrite, sodium silicate, phosphate, some organic acids, not easy to rinse with corrosion inhibition of surface active agents, hexavalent chromium, formaldehyde, strong adsorption of organic solvents.

Considering that there are many loopholes in the electroplating production process, our technicians have improved a set of technological processes for removing oil and rust of metal before electroplating:

Weak alkali cleaning → washing → weak alkali cleaning 2→ washing → washing → vacancy → vacancy → pickling degreasing and activation → acid degreasing and activation → washing → washing → weak acid degreasing and activation → washing → washing → washing → deplating

Detailed process step by step:

1. Weak alkali cleaning 1:

Process requirements: ultrasonic cleaning, the temperature is about 30℃, can use non-ferrous metal cleaning agent, the concentration of 3%. Main functions: to remove dust, oil stains, processing coolant, hand sweat, inorganic salt, etc. Because the solution is easy to dirty, as a pretreatment, often remove.

2. Weak alkali cleaning 2 and 3:

Process requirements: ultrasonic cleaning, weak alkali cleaning 2 temperature 45-55℃, weak alkali cleaning 3 temperature 35-45℃, can be used to clean heavy oil, the concentration of 3%. Main function: to remove polishing agent, difficult to remove oil, inorganic salt and so on. Weak alkali cleaning 2 easy dirty, weak alkali cleaning 3 should not be dirty.

3. Acid degreasing activation:

Process requirements: use acid degreasing agent 2-3% concentration, organic acid 1-2% concentration (self-purchase). The normal temperature. Main function: to remove the metal surface internal oil, especially non-ferrous metal surface internal oil, alkali and oxidation passivation layer, and the initial activation of the metal. Thoroughly remove all kinds of dirt on the surface of the workpiece. Liquid medicine does not stain easily.

4. Weak acid activation:

The compound organic acid (from purchase) was prepared at the concentration of 1-2%, and the wetting agent was 0.5%. Organic acids are not required to have any adverse effects on the bath and coating. Main functions: remove the natural oxidation layer in the washing process, and reduce the formation of oxidation layer.

In a word, the process recommended above is suitable for the treatment of various materials, saving liquid medicine and energy, and can remove all kinds of oil stains. At the same time, the type of oil remover can be changed according to the oil pollution situation. If the copper parts are treated at the same time to prevent copper disintegrating on the surface of brass, steel, zinc and other metals during activation, copper disintegrating substances should be changed or added to prevent copper disintegrating.