Waterborne industrial paint is a type of coating that uses water as the solvent. It has the advantages of non-toxic, environmentally friendly, odorless, less volatile matter, less flammable and explosive properties, and can be used without organic solvents as diluents. It is a green and environmentally friendly product. The application of water-based industrial coatings started relatively late in China, but with the continuous improvement of national environmental regulations and the improvement of environmental awareness among coating companies and the public, the use of water-based and other environmentally friendly coatings is imperative.
However, due to various reasons, some problems often arise during the construction process of water-based industrial coatings due to complex factors related to environment, technology, construction, and other aspects. When encountering these problems, we should still analyze the reasons in a timely manner, solve the problems, and avoid the same problems from happening again. We have specifically collected and summarized some common problems and corresponding technical solutions below, hoping that these contents can provide assistance for everyone in the production and construction process of water-based industrial paint.
1、 Protuberance
Uplifts are also known as wrinkles. During the spraying process or during the drying process of the paint film, the protrusions formed in some areas due to the expansion of the paint surface may take on different shapes.
Cause of formation:
1. The bottom layer was not thoroughly cleaned, for example, the oil or wax on the surface of the bottom layer was not completely removed, resulting in the inability of the re sprayed coating to adhere due to the interlayer effect.
2. The interval between secondary spraying is too short, which does not provide sufficient drying time for the underlying coating, resulting in moisture erosion in the wet paint surface and softening of the primer or topcoat.
Correction method:
If the imprint is obvious, the coating layer should be polished off and re sprayed.
2、 Sagging
Also known as shedding tears or weeping. The coating thickens locally and appears in a teary state due to gravity, only appearing when the sprayed surface is perpendicular or vertically sprayed.
Cause of formation:
1. Improper use of spray guns. For example, if the compressed air pressure is too low, or the distance between the spray gun and the spraying surface is too close, or the movement speed of the spray gun is too slow, it will increase the possibility of sagging. The shape and pressure of the spray beam should be adjusted appropriately to maintain a spraying distance of 20-25cm, and the movement speed of the spray gun should be uniform. Grasp the maximum spraying amount that can cause sagging, focus on observing the formation of the paint film while spraying.
2. The temperature in the spraying workshop is too low, and the paint layer sprayed is not easy to dry, or the paint layer sprayed at once is too thick, resulting in slow drying speed of the paint layer.
Correction method:
When the sagging phenomenon is mild, wet polish the defective area with fine sandpaper after the paint surface is dry. When the sagging phenomenon is severe, polish the defective area before repainting.
3、 Wet printing or wax marks under coating
From the surface of the paint layer, the contour of the bottom layer with contaminated areas or the appearance of various shapes of matte spots can be seen.
Cause of formation:
1. Before spraying, the underlying surface was not thoroughly cleaned, such as oil or wax substances were not thoroughly removed.
2. The previous paint layer is dry or the defects in the old paint layer are not removed.
Correction method:
If the imprint is obvious, the coating layer should be polished off and re sprayed.
4、 Watermarks
White or yellow corrosive spots appear on the surface of the paint layer, mostly on surfaces perpendicular to sunlight such as the roof, engine compartment lid, or luggage compartment lid.
Cause of formation:
1. The coating layer came into contact with water droplets, especially water with high mineral content, without sufficient drying. After mixing with the water in the paint, water droplets will seep into the paint surface, leaving water marks. Therefore, the newly sprayed paint surface is strictly prohibited from coming into contact with water and driving on rainy days.
2. Even on dry paint surfaces, frequent contact with water droplets can leave water marks on the paint surface. Under sunlight, water droplets have the transmission and focusing function of a magnifying glass, and after drying, they will leave white or yellow corrosion contours on the paint surface.
3. If the sprayed paint surface is too thick, it will prolong the drying time and have a greater chance of leaving water marks when the paint surface comes into contact with water droplets.
Correction method:
Use a finer or coarser polishing agent for polishing, depending on the depth of the water mark. In cases where water marks are particularly severe, they will reappear after polishing for a few days. Multiple cleaning should be repeated to completely eliminate water marks. If the cleaning is ineffective, the area with water marks should be wet polished with fine sandpaper and repainted.
5、 Walking silk
The silver powder has uneven reflection. The silver powder particles are arranged in the same direction, presenting alternating stripes of light and dark. If wire walking occurs on a vertical surface, in most cases, the deposited silver powder will puncture the paint film.
Cause of formation:
1. Silver powder paint is a mixture of pigments, moisture, metal particles of a certain size, and additives. The distribution ratio of metal particles within the pigment will affect the color of the paint surface. If the silver powder paint is not thoroughly stirred before spraying, metal particles will deposit at the bottom of the container, causing too many metal particles in the bottom coating, making the paint film too thick and causing uneven paint color.
2. The application viscosity of the coating is incorrect, which means there is an issue with the dilution ratio. If the dilution viscosity is too high, it will lead to wire loss and metal ion aggregation. If the viscosity is too low, the paint film will become too thin and its performance will deteriorate. Therefore, it is necessary to choose a suitable viscosity that can meet both requirements.
3. The time interval between each spraying is too short. If the silver powder paint is not fully dried, there will be uneven distribution of metal particles.
4. Improper adjustment of the spray gun or poor painting technique. Low compressed air pressure, or the distance between the spray gun and the spraying surface being too close, or the uneven movement speed of the spray gun, can cause the silver powder paint surface to appear dark and alternating.
Correction method:
Grind the paint surface with fine sandpaper and spray it again, or increase the compressed air pressure after the paint surface is completely dry, increase the distance between the spray gun and the spraying surface to 40-50cm, and then spray a layer of silver powder paint that is quickly drying.
6、 Fisheye
Also known as shrinkage or bead hole. Circular small pits appear on the paint surface, sometimes in a dispersed or clustered shape.
Cause of formation:
1. The surface of the primer is contaminated, such as oil on the primer. Therefore, it is necessary to clean the sprayed surface before spraying, and a neutral cleaning agent can be used.
2. Strictly filter the compressed air used in the spray gun to ensure its purity, as silicone compounds are often found to come from compressed air pipelines rather than coatings. Evacuate and clean the compressed air filter every day to remove moisture and dirt from the filter, and drain the air compressor every day.
Correction method:
Remove the affected area and repaint.
