When the coating is not properly adjusted, it will cause problems during spraying, which will affect the quality of surface treatment. Following is a list of some problems commonly encountered in the painting process and solutions to the problem.
- Sag: Overdilution.
- Cracking: The curing agent is used too much not properly matched.
- Orange peel: Add too much or less curing agent.
- Pinhole: too much curing agent, too high viscosity, etc.
Causes and fix of coating problems
1- sag
Overdilution. The coating is too thick at one time, the surface is uneven, unclean, complicated in shape or oily. The nozzle is too big or too close to object surface. Improper spraying speed.
Solution
Reduce the dilution ratio. Spray a few more times to avoid overcoating at one time. Sand object surface properly. Select a suitable spray nozzle according to coating properties. master the spray speed according to the paint viscosity.
2- cracking
The curing agent is used too much and not properly matched. The coating is too thick, the surface is dried but the inner layer is not dry. The base layer is unclean, improperly handled, and it takes a long time to stand after polishing. Base and top coat are not properly matched.
Solution
The paint is not fully mixed before application, the upper layer is less lacquered. So we need to mix well according to the required ratio (it is recommended to use a pneumatic mixer), each coating layer should not be too thick. Substrate should be properly handled, the wait time of next coating should not be long. Primer and topcoat should be matched.
3- orange peel
Curing agent is added too much or too little. Thinner is improperly matched. The spray pressure is too high or nozzle is too close to object surface. The environment temperature is too high or too low.
Solution
Mix curing agent in correct ratio. Control the thinner ratio. The pressure should not be too high and the distance is not too close. Pay attention to environment temperature.
4- pinhole
The curing agent is added too much and the viscocity is too high. Environment temperature is too high. The painting pressure is too high and wait time between two layers is not enough. The nozzle pressure is too high but nozzle diameter is too small, too close to the object surface.
Solution
Paint mixing time is too short. Adjust the construction viscosity and master the paint ratio. In summer high temperatures condition, we should reduce the curing agent and add thinner. If we spray twice, it should be re-coated after flash off the base paint. Select the appropriate nozzle, the pressure should not exceed 4kg/cm, and the spraying distance should not exceed 25cm. Stir well and let stand for 10-20 minutes.
5- bubbles
The surface moisture content is high and temperature is high. The air compressor or tube has moisture. The paint is poorly sealed to object surface.
Solution
Dry object surface(preheat before spraying). Use water/oil separator on compressor. Choose a good quality paint. It is advisable to spray twice(flash off the first paint layer then paint again).
6- partial loss of light
Thinner is not enough or not matched to paint and too fast drying, or coating layer is too thick. The base surface is rough and uneven. The construction environment temperature is too low and humidity is too high.
Solution
Use a suitable ratio thinner and master the paint layer thickness. Increase thinner ratio in summer. Object surface should be properly grinded and primer well polished. Ensure the temperature and humidity meet the operation requirements.
7- granulation
Mix in impurities. Spray new paint before spray gun is properly cleaned. The nozzle pressure is too big and nozzle diameter is too small, spray distance is too big from the object surface. The paint is left for too long time after adding thinner but not well mixed.
Solution
Keep the construction environment clean. Different types of paints should be seperated. Select the appropriate nozzle diameter and the spraying distance should not exceed 25cm, the placement time should not be too long and thinner should not be too much, fully mixing before spraying.
