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What are the requirements for metal cleaning agents?

2018-06-08

The national automobile industry is developing at a rapid pace, and the market demand potential is huge. In the production and processing of auto parts, the maintenance and cleaning of metal parts of equipment is an important part. With the development of industrial cleaning agents and the increasing awareness of environmental protection, people have put forward higher requirements for cleaning agents and cleaning equipment. The following small series introduces the application of environmentally friendly industrial cleaning agents to automotive parts cleaning agents.

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（一）

General requirements for environmentally friendly metal parts cleaners

The first is that the cleaning equipment and the parts to be cleaned are not corroded, and the cleaning process does not produce residues, including insolubles, dirt, and coatings that are not conducive to subsequent processing. Next is the cleaning efficiency is high, and the cleaning is thorough enough. Finally, it requires low cost, meets environmental protection requirements, is harmless to the human body, and has a relatively mild odor.

In the metalworking industry, as people's requirements for zero performance and processing efficiency are getting higher and higher, cleaning agents are no longer pure decontamination, but are given more requirements. According to the characteristics of the metal material, it is required that the cleaning agent used can effectively decontaminate, and also needs to have an anti-rust effect on the surface of the metal component, and enhance the corrosion resistance of the product, etc., which is added to the cleaning agent. The agent puts forward higher requirements.

（二）

Classification of cleaning equipment and requirements for cleaning agents

Currently used metal cleaning equipment includes immersion cleaning equipment, spray cleaning equipment, high pressure spray cleaning equipment and ultrasonic cleaning equipment.

Intrusive cleaning is generally used for multi-cavity parts. This method has high requirements for the cleaning ability of the cleaning agent and the ability to emulsify the miscellaneous oil, but the defoaming performance is not high. However, a cleaning agent having a strong emulsified oil has a disadvantage, and the cleaning ability is gradually lowered, so that the service life is short.

When cleaning the parts in the automobile gearbox, the through-type spray cleaning method is mostly used, and the washing and drying are also carried out after the cleaning. Spray cleaning equipment is generally equipped with an oil skimmer, which is suitable for using a cleaning agent with strong resistance to miscellaneous oil, and also needs to consider the defoaming ability. The cleaning agent has its own optimal operating temperature range, and its cleaning ability increases with temperature, but once it exceeds this range, the cleaning ability will decrease. So it is also important to have a proper cleaning temperature.

High-pressure spray cleaning is often used to remove dirt on the surface of parts and to remove burrs on the metal surface. The parts are often positioned and sprayed at a fixed point. The cleaning agent is required to have good resistance to foam under high pressure.

（三）

Requirements for cleaning agents in subsequent processing steps

Under certain process conditions, the choice of cleaning agent must also consider the impact on subsequent processing steps. For example, in the production of gearbox gear parts, there are two steps in the machining process that require grinding and shot peening. After the two processes are completed, the gears need to be spray cleaned. Then, in the middle cleaning between grinding and shot peening, it is necessary to consider whether the cleaning agent used will affect the subsequent shot peening process, for example, whether it will leave on the surface of the part after drying. Sticky detergent residue or cover film, etc. These will destroy the processing quality of the shot peening process, resulting in defects in the product.

（四）

Three-point quality indicator that solvent-based cleaners must achieve

Any type of industrial cleaner is a technical indicator that must be strictly controlled for pH. Especially for solvent-based cleaning agents, the acidity index is more important, because the workpieces to be cleaned are finished products, most of which do not do any treatment. The quality of the cleaning agent directly affects the quality of the workpiece to be cleaned. Therefore, the acidity index represents the stability of the cleaning agent and the quality assurance of the workpiece being cleaned. Usually, the stabilizers or antioxidants added at the time of shipment are as follows: phenols, alcohols and epoxy compounds, etc., and the addition amount is generally within 0.05% to 5%. The acidity at the factory is controlled within 10ppm (0.001%). The acidity is tested according to the provisions of GB4120.3, equivalent to the international standard ISO-1393, using acid-base titration. Since many cleaning agents do not dissolve in water, they cannot be titrated with an alkali solution, but a water washing method is used to titrate the aqueous liquid washed from the solvent cleaning agent. This method is more cumbersome. An absolute ethanol lye method can also be used for direct titration because many industrial cleaners are dissolved or partially dissolved in ethanol. This method is convenient for inspection in the construction workshop.

Moisture content in the cleaning agent

The water content of solvent-based cleaners is also an important indicator. In principle, the less water, the better, but it is impossible to produce completely water without mass production and use, and each solvent has a certain water content. Some are completely miscible with water, such as lower alcohols, ketones and some ethers; some have certain saturated solubility at certain temperatures, such as hydrocarbons, fluorocarbons, chlorocarbons and bromines, etc., and water exceeds saturated solubility. The delamination occurs and the stabilizer in the solvent is pumped into the water layer to deteriorate the stability of the solvent (cleaning agent). At the same time, water exists, and free F ˉ, Cl ˉ and Br ˉ ions in the cleaning agent form acid with water, forming a vicious circle during heating, and the acidity is getting higher and higher. Therefore, the acidity and moisture in the cleaning agent are two interdependent indicators that directly affect the quality of the cleaning workpiece. If some of the workpieces are cleaned, they lose their luster or leave water marks on the workpiece, which is related to acidity and moisture. At present, the solvent-based cleaning agent produced at home and abroad has a moisture control within 100 ppm (0.01%). The determination of trace moisture is carried out in accordance with the provisions of GB6283-86. The Karl Fischer method. A simple cloud point method can also be used, that is, according to the provisions of GB4120. Gas chromatography can also be used for analysis. From the scientific rigorous point of view, the absolute value of the water content of the solvent of our company Wuyang Chemical can not be zero, but it is negligible.

Nonvolatile matter super indicator residue

The amount of non-volatiles in the cleaning agent directly affects the cleanliness of the cleaned workpiece. Since the cleaned workpiece is immersed in the cleaning solution and then allowed to dry naturally, the non-volatile matter in the cleaning solution may adhere directly to the workpiece. If it is an electronic component, it will affect its electrical performance, especially for microcircuit devices such as PCB boards. The number of ions attached to the board is measured in μg per square centimeter (NaCl μg/cm2). The lower the requirement, the better. Generally, it is controlled below 10ppm at the time of shipment. This is an enterprise standard for producing single solvent type cleaning agents at home and abroad. The detection method is carried out in accordance with the provisions of GB6324.2-86. Similar to the method of ISO 759-1981. A simple detection method is to drop a few drops of the cleaning agent on the glass lens to let it spontaneously volatilize, and to observe the residual trace on the lens, the amount of non-volatile matter of the cleaning agent can be roughly judged. Of course this is only a qualitative test.

Toxicity controllability

Toxicity is an important indicator of whether a cleaning agent can be used. Although it has no direct impact on the cleaned workpiece, it has a profound impact on humans and the environment, and it is also a major factor in whether we choose it today. The toxicity of the cleaning agent is determined on the basis of animal experiments and correlations with human physiological experiments. Strictly speaking, any chemical solvent is toxic, just the size. The size of the toxicity and the safe range of the human body and the precautions are taken only through rigorous animal experiments. That is, the amount of animal per kilogram of body weight can withstand. Although many chemical predecessors have done relevant toxicity tests, it is well documented, but the current cleaning agents are not pure, and the data on the data can be used for reference. The mixture only passes real animal experiments to determine the safe concentration range, establishing safe protection measures and precautions for producers and users. Toxicological experiments were mainly conducted by oral and inhalation experiments. The amount of LD50 in the acute oral toxicity test of rats, that is, the greater the semi-lethal dose, the lower the toxicity; the same amount of acute inhaled LD50 in rats, that is, the greater the semi-lethal dose, the allowable concentration of the workpiece environment The higher. Based on these measured data, safety standards and protective measures for the workpiece location of the cleaning agent can be formulated. Toxicological tests should be carried out by the health prevention department. Conduct and price according to the provisions of GB1560-1995 or GB5044-85. Wuyang special hydrocarbon cleaning agent is halogen-free, does not contain n-hexane, and is RoHS compliant. Used to remove various oils from metal contamination during industrial processing to meet subsequent processes. It has excellent effects in removing residual grease such as lubricating oil and cutting fluid.