Coating problems and countermeasures of water-based paint in the field of modified cars!

At present, the production market of modified vehicles in China (including special vehicles such as fire trucks, oil tankers, cement mixers, dump trucks, rescue vehicles, and sanitation vehicles such as sprinklers, garbage cleaning vehicles, and sweepers) is developing by leaps and bounds.

Since the modified vehicles are mainly operated outdoors, in the environment of wind and sun, high humidity and heat, large temperature difference and poor road conditions, the decoration and protective performance of the coating are required to be higher

Based on the characteristics of water-based coatings and application cases, this paper briefly discusses the coating problems and countermeasures of water-based coatings in the field of modified vehicles

As the saying goes, three parts paint, seven parts construction

1.

In addition to the problems of the primer itself, the factors that affect the adhesion between the primer and the substrate include the following aspects:

1. Residual cutting fluid, oil and other oils from the pretreatment of the substrate have different compatibility with the water-based paint and affect the adhesion

2. Some processes use cold-rolled sheets, galvanized sheets, and the surface of the substrate is directly primed without grinding.

   
   

3. Spray primer or intermediate paint on the electrophoretic bottom.

   
   

For the above common problems, if you do not change the existing process of the customer, you can only work hard on the product, and prepare corresponding products for different substrates and processes to meet the needs of customers, so as to achieve customer satisfaction.

2.

Whether it is a different modified model or a trailer model, the coating process is inseparable from scraping and leveling, with partial scraping and full scraping.

3.
Interval time of composite coating

Some large-scale modified car factories have large orders and fast production pace.
They have high requirements on the drying speed of painting and coating and the overcoating time of more than two coats.
They hope to be able to spray without interruption to increase their output.
, and the two-component product has certain requirements for the interval time when painting.
The interval time is short, which has a certain impact on the adhesion, hardness, smoothness of the topcoat, and gloss.
Efficiency and effect will be much better, but more customers require coating efficiency without baking.
It is difficult to fully meet customer requirements for this problem.
We can only improve work efficiency and shorten the overcoating interval.

.

Fourth, the effect of temperature and humidity on the paint film in the coating environment

At present, the water-based coating process for refitted vehicles is mainly divided into two-coating method and three-coating method (as shown in Figure 1).
The paint has no drying application method, as shown in Figure 2) and conventional application method (conventional application method with primer drying, as shown in Figure 3)
.
For the wet-on-wet construction process, although the construction efficiency can be improved, it is still a difficult point for water-based coatings.
At the same time as rapid construction is required, the primer is dry and the reaction is incomplete, which often reduces the performance of the coating.
, at the same time accompanied by defects such as poor adhesion, pinholes, cracking, loss of gloss, color loss, prickly heat and so on
.
Therefore, the wet-on-wet process often requires the formulation and construction process to be adjusted to achieve the best performance that meets the on-site process requirements
.

The climate varies greatly across the country, and the temperature and humidity difference has a great impact on the construction, especially in the north, the winter is long, and the subzero temperature is relatively long, which has a great impact on the transportation and construction of water-based paint.
In the south And coastal areas have high humidity all year round, the rainy season is long, high humidity has a great impact on the drying speed, and the release cycle of the paint film performance is long, and it is not easy to satisfy customers who need drying and hardness in a short time.
Will cause sag, flash rust, orange peel and other problems
.

There are two solutions to this problem: one is to change the coating environment, increase the equipment to adjust the temperature and humidity, and try to maintain a suitable coating environment; the other is to change the adaptability of the paint to the environment and improve the drying speed of the paint.
Strengthen the wetting and flash-drying effect, improve the sag resistance, and alleviate the construction problems in high-humidity environments.
In addition to the above-mentioned improvement directions in low-temperature coating, the anti-freezing ability of the paint liquid should be increased to solve the hidden danger of transportation.
Of course, when When the temperature reaches below zero, the above methods are also ineffective, and it is necessary to keep warm and increase the temperature of the construction environment to solve the problem
.

5.
Cause analysis and solutions of common defects of paint film 1.
Sagging

Abnormal state: a, the workpiece is wet and sprayed, and there is sagging; b, the sagging caused by the worker's gesture problem; c, the sagging caused by the large ambient temperature difference and high humidity; d, the sagging caused by the wet-on-wet process

Improvement measures: a.
Preheat the workpiece and spray it after drying; b.
Adjust the worker's gesture to increase the worker's proficiency in spraying water-based paint; c.
Adjust the amount of water added in time according to the temperature, strengthen air circulation or add a dehumidifier; d.
Need Adjust product matching or improve product

2.
Shrinkage

Abnormal state: a, the substrate and primer are contaminated with sweat or other pollutants, such as wax, kerosene, silicone oil, engine oil, water, etc.
; b, compressed air is mixed with oil and water

Countermeasures for improvement: a, thoroughly clean the substrate or primer, the contamination on the surface of the putty layer; b, check the oil-water separator and clean the compressed air

3.
Loss of light

Abnormal state: a, slow drying, high humidity, the surface absorbs water and whitens, causing loss of light; b, adding too much water and spraying too thin, resulting in poor plumpness of the coating; c, the putty layer is not smooth, and the mirror effect of the coating is poor; d.
Wet-on-wet process leads to loss of light

Improvement measures: a.
Control the ambient temperature to strengthen ventilation, and add dehumidification equipment if necessary; b.
Adjust the viscosity of the paint solution and product performance; c.
Strengthen the control of the grinding station of the putty layer; d.
Adjust product matching and product performance

4.
Poor adhesion

Abnormal state: usually occurs between the adaptation of the primer and the substrate material, between the putty layer and the topcoat

Improvement measures: Test and adjust the compatibility of primer and topcoat according to the variety and quality of substrate material and putty used by each manufacturer

5.
Prickly heat

Abnormal state: a, when there is baking, the baking temperature is set too high, and the leveling time before entering the drying room is too short; b, the temperature at the entrance of the drying room is too high; c, the spraying is too thick, and the ambient temperature is too high; d, Product additives boiling point too low

Improvement countermeasures: a, adjust to the appropriate temperature when the product is cured, and increase the leveling time; b, set the drying room temperature to the mode of low-medium-high-medium-low; c, adjust the spray thickness and interfere with the excessively high ambient temperature; d.
Adjust product performance

6.
Granules

Abnormal state: a, there are foreign objects such as dust on the surface to be sprayed; b, the construction environment is poor, and there are a lot of dust particles in the air; c, the paint is mixed with foreign objects or diluted with unclean water; d, the environment in the drying room is poor, Circulating wind causes wanton dust

Improvement measures: a, clean the surface to be sprayed; b, clean up the construction area before get off work every day; c, keep the paint clean and dilute with clean deionized water; d, clean the sanitation in the drying room every day

 The above briefly introduces the construction process, common problems and solutions of water paint for modified vehicles
.
There are many factors that affect the performance of water-based coatings on site.
The product formulation and construction process need to be adjusted according to the site conditions to ensure the best performance
.