Types of construction primers and their scope
The better prepared the base, the better and more durable its finish will be. This rule is known to all builders.
And one of the main and most important stages of preparation is priming. What is it, why is it necessary and what types of primer exist, we will tell in this article.
The content of the article
The role of primers in surface preparation
Any surface that needs to be finished, whether it is plaster, wood, metal, brick or concrete, requires giving it certain properties that provide good adhesion to the subsequent layer. If it is loose, cracked, too smooth or predisposed to excessive absorption of moisture, then neither paint, nor putty, nor other coatings and mixtures will stick to it.
It is to eliminate such properties, as well as to give the base increased resistance to external influences, primers are used (seeWhy do we need a primer: technological nuances of finishing work) - the types of such compounds are very diverse, which allows you to choose the one that will solve the whole complex of tasks required in a particular situation.
For reference. For example, a primer can protect wood from decay and damage by bugs, metal from corrosion, and walls in damp rooms - from the spread of mold.
In addition, the primer layer provides uniform overlay and distribution of the finishing compounds on the surface, reduces their absorption, facilitates the work. In a word, there is no doubt that in most cases a primer is simply necessary - which is better, this is another question that we will try to understand.
How to choose a primer
To understand what primer you need, you need to know what it is. If we talk about the types of primer can vary in scope and composition, base material. They can be ready to use, concentrated or in the form of dry mixtures, requiring dilution with water or a solvent with your own hands.
If in the recent past the choice was not particularly great, today many specialized compounds have appeared, in the variety of which it is no wonder to get confused. Common to them is the presence in the composition of substances that, when dried, form a durable film on the treated surface. It can be oils, various types of glue, natural and synthetic resins, etc.
In addition, various additives can be introduced into the primer - pigments to control the quality of application, drying accelerators, fungicides to prevent the development of mold, etc. But they are classified primarily on the basis material.
Classification based
The composition of the mixture applied to the base should correspond to the material, improve its properties. You should also consider what kind of coating it is prepared for.
When choosing which primer is better, first of all pay attention to its basis:
- Mineral-based primers, the main bonding component of which is cement, are used for preliminary leveling and primary processing of surfaces made of concrete, expanded clay and gas-silicate blocks, bricks.
- Compositions based on acrylic copolymers can be considered universal, they are suitable both for mineral substrates, including plastered and puttying, and for wood, including wood-particle and wood-fiber boards. Their main advantages are lack of smell, environmental friendliness, short drying time and low price.
Note. Acrylic primer is not recommended for use on metallic surfaces. It contains water, which causes corrosion and the appearance of rust.
- Primers on alkyd binders are used for the treatment of metals and wood (seePrimer wood - process features) The surface of the wood swells under its influence and becomes susceptible to any finishing compounds.
For the primer of metals, such compositions must be selected depending on the type of future coating. If the base is zinc chromate, they have a wide range of applications, but the zinc phosphate primer will be an excellent corrosion protection for alkyd paints. Alkyd primer is not suitable for mineral surfaces.
- Also, for the processing of wood and metal, phenolic and glyphthalic compounds are used. The latter are used only for indoor work in dry rooms.
- The polyvinyl acetate primer has a fairly narrow range of applications and is the best substrate for polyvinyl acetate paints. This is the fastest-drying composition of all existing - half an hour is enough to completely dry the layer.
- Perchlorovinyl compounds are quite versatile - they are suitable for both metal and mineral (brick, concrete, plastered) substrates. Easy to apply, quickly dry even at a fairly low temperature, but the instruction prohibits using them for internal work due to high toxicity.
- Harmful substances are also found in polystyrene primers used for application on wooden and plastered surfaces, therefore they should be used only outside or in well-ventilated rooms.
Also, adhesives can be used as a primer. Often its role is played by PVA glue diluted with water or any wallpaper glue.
Of course, they are able to limit the absorbent properties of the surface, increase its adhesion, but they will not be able to cope with other tasks - strengthening, protection from the appearance of colored spots, providing water-repellent properties, etc.
Therefore, it is better not to save on such material as a high-quality primer, the types of which you now know.
Application Classification
If everything is clear with the base material, it is clear which composition on which binder will be most effective in a particular case, now we need to talk about the state of the surface being treated and the conditions in which it will be used. This is a very important point in determining which primer is better - which is worse.
So:
- If the treated surface is fragile, crumbling, porous, and easily absorbs moisture, a deep penetration primer must be applied to it. It will strengthen the base a few centimeters in depth, reduce absorbency, and save on subsequent finishing.
- Strengthening primers possess approximately the same properties, but penetrate to a shallower depth. They are good, for example, for preparing for drywall finishing - they impregnate and fasten the upper paper layers, normalize the absorbent properties of the material.
- If the base does not absorb moisture, is strong, dense and very smooth (tile, glass, plastic, etc.), it is necessary to increase its ability to adhere to the finishing layer. To do this, apply an adhesive primer.
- Primers for special purposes are designed to protect surfaces from harmful external influences. They introduce special additives that can reduce the influence of harmful factors.
For example, if there is a risk of fungus formation, antiseptic formulations are used (seeAntifungal primer - purpose and characteristics of the material), if it is necessary to protect the metal from rust - anti-corrosion, etc.
In a word, when choosing a product, you need to look so that it approaches the surface material, levels its negative properties, creates a good basis for the finishing layer and serves as protection against harmful factors.
Conclusion
In this article, we did not address the issue of the rules and methods of applying a primer. This is described in detail in other materials on the site and on the video.
As for the choice, it will be easy to make it without special knowledge - all information about the purpose, properties and scope of application is always indicated on the package.
