In the modern construction and automotive coating industry, high build primer is a key coating step. This type of primer is usually used to provide a thick coating, fill surface defects and prepare for the topcoat. During the construction process, the accurate mixing ratio directly affects the thickness, adhesion and final performance of the primer.
This article will explore the mixing ratio of high build primer, its functions, precautions for use and how to ensure construction quality.
What is high build primer?
High build primer refers to the type of primer with a thicker coating in the coating. It is mainly used to repair surface defects such as scratches, dents, sandpaper marks, etc. High build primer is widely used in the fields of automobile repair, ship maintenance, and architectural coating. Compared with ordinary primers, it has a higher solid content and can form a thicker coating layer after application, reducing the need for multiple spraying. The main goal of this type of primer is to make the coating surface smoother, reduce the time and effort of the sanding process, and ensure a more perfect coating effect of the topcoat.
Main functions of high build primer
● Filling surface defects: The thickness of high build primer can help fill minor surface defects, such as small scratches, dents, etc., to lay a solid foundation for subsequent painting.
● Enhance adhesion: One of the main functions of primer is to enhance the adhesion of the topcoat, so that the topcoat and the substrate form a good bond.
● Increase coating thickness: By spraying high build primer, the thickness of the coating can be increased, thereby reducing the consumption of topcoat and making the coating more durable.
● Isolation effect: Primer can also act as an isolation layer to prevent stains, grease or other contaminants on the substrate from affecting the final effect of the topcoat.
What is the mixing ratio of high build primer?
Before using high build primer, the correct mixing ratio is crucial. The performance, leveling and curing effect of the primer all depend on the accuracy of the ratio. For most high build primers, manufacturers will provide clear ratio recommendations, which are usually detailed on the label. However, according to different types of primers and application requirements, common mixing ratios can be roughly divided into the following categories:
Common ratios of two-component high build primer
Two-component high build primer is a more common type, and its main components are primer and hardener. The usual mixing ratio is 4:1 or 5:1, that is, four or five parts of primer correspond to one part of hardener. This ratio helps the primer cure quickly and ensures a strong and smooth coating.
For example:
● 4:1 ratio: means that 1 part of hardener is mixed for every 4 parts of primer. If you need to mix 1000 ml of primer, you need to add 250 ml of hardener.
● 5:1 ratio: means that 1 part of hardener is mixed for every 5 parts of primer. This ratio is suitable for primer types with higher solid content, usually for thicker coating requirements.
After mixing the primer and hardener, it is usually necessary to add an appropriate amount of diluent according to the temperature and humidity conditions to adjust the fluidity of the paint. The proportion of thinner is generally between 10% and 20%, but the specific amount needs to be adjusted according to the type of primer, environmental conditions and requirements of the spraying equipment.
Ratio of single-component high build primer
Single-component high build primer does not require hardener to be mixed, and it can be used by adding a proper amount of thinner. This type of primer is easier to apply and is suitable for less complicated painting tasks. For single-component primers, the common dilution ratio is 5%-15%, but the specific dilution ratio depends on the spraying conditions, surface conditions and the required coating thickness.
Dilution ratio of high build primer
Whether it is a single-component or two-component primer, it may be necessary to add thinner. The main function of the thinner is to adjust the viscosity of the primer to ensure that the surface can be evenly covered without sagging or particle problems during spraying. The proportion of thinner needs to be adjusted according to the type of spraying equipment, coating thickness requirements and ambient temperature. It is generally recommended that the dilution ratio be controlled between 10%-20%, but if it is a high temperature environment, the amount of thinner may need to be increased to prevent the paint from curing too quickly.
What are the steps for using high build primer?
To ensure that the coating effect of high build primer reaches the expected level, every step in the construction process is crucial. From surface treatment to mixing of primer to actual spraying, each step needs to be carried out strictly in accordance with the operating specifications.
Surface treatment
Before using high build primer, surface treatment is a crucial step. Whether it is metal, wood or concrete surface, it needs to be thoroughly cleaned to ensure that the surface is free of dust, oil or rust. For metal surfaces, sandblasting or grinding is usually required to enhance the adhesion of the primer. If the surface is not properly prepared, even high-performance primers will find it difficult to play their due role.
Primer mixing
Mix the primer and hardener in the recommended proportion according to the ratio provided by the manufacturer and ensure that they are stirred evenly. If dilution is required, the amount of diluent should also be controlled within the recommended range to ensure that the viscosity of the primer is suitable for spraying.
Spraying process
The spraying of high build primer is usually carried out with a spray gun. When spraying, try to keep a uniform speed to ensure that the coating thickness is uniform. For best results, it is recommended to spray at least two to three layers, and wait for the primer to dry before spraying the next layer between each layer. Spraying too thinly will affect the filling effect of the primer, while too thick may cause cracking or sagging of the coating.
Drying and sanding
After the primer is sprayed, it is necessary to wait for it to dry completely. After the primer dries, it is usually necessary to perform light sanding to ensure that the coating surface is flat and smooth, ready for the spraying of the topcoat. It is recommended to use appropriate sandpaper (such as 400 to 600 mesh sandpaper) during the sanding process to avoid damaging the coating.
What are the application scenarios of high build primer?
High build primer is widely used in many fields such as automobiles, ships, and construction, especially in occasions where surface repair and leveling are required.
● Automotive painting: High build primer is an indispensable part of the automotive repair and painting process. After repairing scratches or replacing body parts, high build primer can be used to fill uneven surfaces and ensure perfect adhesion of the topcoat.
● Ship maintenance: Ships are often exposed to humid and seawater environments, and rust and cracks are prone to occur on the surface. High build primer can fill these defects and lay the foundation for subsequent anti-corrosion coatings.
● Construction projects: In the surface repair of concrete or metal structures, high build primer can provide good surface flatness and adhesion for subsequent decorative paint or protective coating.
What are the precautions for using high build primer?
Although high build primer is very powerful, the mixing ratio still needs to be strictly controlled during actual use, because too much or too little ratio of hardener to primer will affect the performance of the coating. Too much hardener will make the primer cure too quickly, resulting in brittle cracking of the coating; too little hardener will make it difficult for the coating to cure completely. In addition, the curing speed of the primer is closely related to the ambient temperature. In a high temperature environment, the primer cures faster, and sagging or particles may occur during spraying; while in a low temperature environment, the primer cures slower, and the drying time between each layer needs to be appropriately extended.
Finally, when using high build primer, the operator needs to wear a protective mask and gloves to avoid inhaling harmful gases or direct contact with the skin. In addition, good ventilation conditions must be ensured during spraying.