How to clean metal

When cleaning metal, you may be worried about the occurrence of rust. There are various cleaning agents and methods available for industrial cleaning, but if the right one is not selected, the metal may be damaged. Let's check what cleaning methods are available.

Metal cleaning methods

There are various types of stains on metals, and there are several ways to remove them. Let's take a closer look at some typical metal cleaning methods.

Strip stains with cleaning agents

This method uses aqueous or semi-aqueous cleaning agents to lift up and remove oil stains. In the case of metal cleaning, alkaline or neutral water-based cleaning agents are often used. However, since water is used, it is necessary to use a cleaning agent within a pH range that will not corrode the metal. Please check the appropriate pH for the target metal. In addition, ultrasonic waves and object shaking systems are often used in combination.

Dissolve stains with organic solvents

A solvent is a liquid intended to dissolve an object (stain). Organic solvents such as petroleum, chlorinated hydrocarbons, coal tar, alcohols, ketones, and phenol are mainly used for metal cleaning. The most common methods are gas phase degreasing using vapor of the above-mentioned materials and liquid phase degreasing using liquid.

Remove stains with a machine

This method physically removes solid stains. A file or non-woven fabric can be used to wipe it off by hand, and a polishing/processing machine or blasting process can be used to make the metal surface smooth.

Decompose stains by chemical reaction

In cases where rust has already occurred, we use a chemical change in which acid decomposes oxides. By filling a cleaning tank with an aqueous solution and dunking the object, it is possible to remove the oxide film from the metal surface.

Metal cleaning with surfactants

Surfactants have the function of mixing water and oil, which would normally not mix with each other. This emulsifying and dispersing action makes it possible to remove dirt that is difficult to remove from metal. In addition, when they adhere to metal surfaces, they form a protective film that prevents metal from rusting. For this reason, surfactant-based cleaning agents are often used to clean metals.

Here is an example. First, place a quasi-aqueous cleaning agent containing a surfactant in a cleaning tank (immersion jet type) and control the concentration to 15% or higher. At this time, it is possible to effectively remove dirt by heating the cleaning agent to a high temperature of about 50 degrees Celsius. Next, drain the liquid, and transfer the material to be cleaned to the pre-rinse tank. Let's further drain the liquid and move it to the two rinse tanks. At this time, the surfactant should be kept at a low temperature of about 40 degrees Celsius, which will have a dispersing effect on the stains and prevent them from re-adhering to the surface. Then, move it to the hot-air drying unit. By rinsing at a low temperature, it is possible to dry quickly.

The above cleaning method can efficiently remove high-soil polybutene resin from aluminum surfaces. It will also be possible to reduce the amount of cleaning agent waste and to regenerate rinse water. However, it is necessary to add a corrosion inhibitor to the cleaning solution to prevent metal corrosion.

Rust-proof cleaning

So, how can we clean metals to prevent them from rusting? Here are some methods.

Metals rust because water + oxygen adheres to metals. Furthermore, the higher the temperature, the faster the rust forms. The following measures are effective in preventing rust formation.

Use organic solvents

Without water in the first place, rust is less likely to form. Cleaning with organic solvents does not require rinsing with water.

Use surfactants

For water-based cleaning, a low-concentration degree surfactant can be added to the final cleaning bath, or the cleaning agent can be left to dry without removing it. The surfactant will act as a protective coating to prevent rust. However, this is only possible if it does not interfere with later processes.

Thoroughly drain + dry

When using a water-based cleaning agent, drain off the liquid thoroughly and dry thoroughly. Spin drying is recommended for plate work. If possible, soak them in rust-preventive oil afterwards to shut off the air.

Fill the dryer with nitrogen gas

Air can be eliminated by adding nitrogen gas. Since oxygen will no longer be supplied, rust will not occur.

Summary

There are many ways to clean metal without rusting it. The most common method is the cleaning method utilizing surfactants. Consider the type of dirt you want to remove and the items to be cleaned, and select the most suitable washing method.