Coating characteristics

There are some simple and practical methods to identify the characteristics of coatings in life. The most economical and easy way is to touch and observe with your eyes. One can determine the characteristics of most coatings by hand, eyes and cheap viscosity cups.

  These characteristics can be accurately tested in the laboratory, but the test equipment is relatively expensive. Although it is primitive to touch, it can make experienced people understand the characteristics of coatings. Note that some paint instructions indicate "Do not touch the skin", so you must take protective measures.

1.Consistency

Put the rod into the coating and stir it. The greater the resistance, the greater the consistency, and vice versa. The resistance of the paint should be uniform, otherwise, it means that the paint is mixed unevenly.

2.Liquidity

When the observation rod is pulled out of the paint, the time that the depressions in the paint are filled up, the longer the time, the harder the paint flows in the system. If the depression cannot be filled immediately, you need to use a pressure vessel with an outlet at the bottom, and configure a squeeze plate in the vessel.

3.Colorability

Use your forefinger and thumb to pinch the paint evenly and try to feel the graininess in the paint. If the particles feel large, it is a coarsely ground coating. If paint remains in the fingerprint after twisting the index finger and thumb, it means that the paint is finely ground. If there is no color on the finger, the paint is colorless. Some paints appear to be colorless, such as semi-gloss, matt varnishes, but they are colored paints.

4.Adhesiveness

Adhesiveness is a property of all fluids, which characterizes the atomizing ability of the fluid. Atomization ability describes how easy it is to break paint into fine particles. After the nitrocellulose paint and enamel paint are diluted, their adhesion decreases. Sometimes the viscosity has little effect on the atomizing ability. For example, greases are very viscous, but they are easily atomized. Therefore, it is precisely the size of the adhesiveness that determines the size of the atomizing ability.

5.Corrosive

The coated material can be immersed in the coating for a certain period of time to observe the effect of the coating on the substrate. The most time-saving method is to measure the pH of the coating. It must be pointed out that different coatings and different substrates produce different results. For example, water has a corrosive effect on carbon steel, but has little effect on glass. Therefore, the substrate and the coating should be considered together. For corrosive coatings, the parts in contact with the coating in the spraying equipment shall be made of stainless steel, plastic or other corrosion-resistant materials.

6, leveling

The leveling ability of the paint sprayed on the surface of the object must also be considered. Different coatings have different leveling characteristics. Some paints can build up on the surface of objects. For example, water droplets flow on the dusty car body surface, while the waxed car body surface is piled up. Some coatings have a similar phenomenon on the surface of some objects.

 7.Viscosity

Simply put, the viscosity of a liquid indicates the magnitude of its flow resistance. The flow characteristics of coatings are directly related to the magnitude of internal friction. Therefore, factors that affect the internal friction of a liquid (such as solvents, thinners, and temperature) will affect the flow characteristics of the liquid. At the same time, the flow characteristics of the liquid determine the difficulty of atomization, the flow capacity on the workpiece and the selection of conveying equipment.

Viscosity is a quantity that describes the flow and shear properties of a coating based on time. It is a numerical quantity. Viscosity, as a very important parameter, is the base point for us to determine the pressure required to make the paint flow in the system. We must make the paint flow through the hose, the nozzle of the spray gun and generate a good atomization. Therefore, viscosity control is an important guarantee to obtain consistent coating quality in daily coating.