Heat-resistant paint for metal: how to choose and where to apply?

Metal is a durable, reliable and refractory material, its properties have been actively used since ancient times. However, under the influence of high temperatures, even the most reliable structures are not strong enough. To reduce the negative effects of strong heat, and ideally block it completely, you need to use protective coatings for the metal. In such cases, a special heat-resistant paint is of great importance.

Fire retardant paint has a varied level of protection, special properties and application nuances. There are two main categories: intumescent and non-bloating colorants. The second type is very expensive and not too much in demand.

Protective parameters are achieved due to reagents that belong to one of three groups:

• containing nitrogen;
• containing phosphoric acids and derivatives of these acids;
• polyhydric alcohols.

Fire protection paints are 40-60% of these components. Under normal conditions, they work as a standard paint and varnish coating, and as soon as the temperature rises, the generation of gases begins. A layer of coke forms, which reduces the effect of the heat. Despite the identity of the principles of work, paints can have a different chemical composition from each other.

So, on the basis of nitrogen, substances such as melamine, dicyandiamide and urea are often created - they make the paint less wearing out. The main polyhydric alcohols used by professionals are dextrin, dipentaetrine, pentaerythritol and starch. In addition to preventing burnout, alcohols enhance the adhesion of heat-resistant paint to metal.

Phosphorus-containing acids also improve adhesion to the surface, guarantee the durability of the paint and varnish composition. When a fire starts, swelling occurs very quickly and intensely. As a result, the formation of smoke is reduced, smoldering and burning are significantly slowed down. The main components containing phosphorus in paints are: ammonium polyphosphate, melamine phosphate, various salts and ethers. Any standard fire-retardant substances do not emit poisonous gases during a fire, therefore they are considered as safe as possible.

In normal situations, fireproof paint does not differ much from the standard one, the difference begins to appear only with a significant increase in temperatures, when the surface layer is heated. This circumstance becomes a catalyst for the synthesis of porous oligomers and their curing. The speed of the processes is determined by the nuances of the chemical composition, the features of the application and the degree of heating. The process itself will be like this:

Refractory paint gives off gaseous products, which start the subsequent process and prevent the temperature from destroying the coating layer. Phosphoric acid is released, forming coke foam. The foaming agent is destroyed, which, under the influence of the rising temperature, is filled with a cushion of gases, which prevents heating.

Chemical decomposition of substances containing phosphorus: the top of the reaction occurs when heated to 360 degrees.

Pyrolysis of network structures. In heat-resistant paint, it starts at 340 and goes on when heated to 450 degrees with intensive foaming of the protective layers.

At a temperature of 200 degrees, the metal is strong enough, but as soon as steel is heated to 250 degrees, it loses its strength very quickly. When heated to high temperatures - 400 degrees and above, the smallest loads can damage the structure. But if you use good paints, you can maintain the basic qualities of the metal even at 1200 degrees. The standard of protection is the preservation of basic qualities up to 800 ° C. How much paint can maintain its qualities is determined by its chemical composition and purpose.

So far, technologists have created 7 categories of fire protection, the differences between them are expressed in the duration of fire resistance. The 7th grade means that the protection works for a quarter of an hour, and the highest level - 2.5 hours. Heat-resistant paint is usually able to withstand heat up to 1000 degrees. It is these coatings that are applied to heating equipment and other heating systems of a similar purpose.

The purpose of high-temperature compositions is to paint radiators and transport engines, the joints of the masonry of brick ovens. If the heating is not too high - as on the parts of a gas boiler - heat-resistant varnishes can be used, which do not lose their appearance at temperatures of 250 and even 300 degrees.

Heat resistant paint can be made from alkyd, epoxy, composite, silicone components. Also, chemists have learned to use ethyl silicate, epoxy ester combinations and a number of dyes based on heat-resistant glass for such purposes.

Since the actual performance of paint products is critical, there are a number of leaders who best protect load-bearing structures. Coating "Thermobarrier" guarantees steel protection up to two hours, the minimum level is three quarters of an hour.

The cost and parameters of paints can vary greatly. "Nertex", for example, it is created on a water basis and reliably covers the structure from high heat.

"Frizol" fully meets the standards of GOST, can have the properties of the second-sixth groups. The time of use of the coating is a quarter of a century, fire resistance meets all the requirements.

Brand protection "Joker" works well, but it is advisable to use it only in rooms where the security level is equal to the second, third or fourth groups.

"Avangard" - the products of the recently appeared company of the same name, but it has already managed to gain solid authority, become famous for its excellent ratio of efficiency and price.

Heat-resistant paints can transform the product into any color. Compositions intended for painting furnaces have an excellent level of corrosion protection, do not deteriorate under the influence of moisture. Mandatory requirements for this group of paints are reliable protection against electric shock and the ability to tolerate contact with aggressive substances.

All the desired properties of the coating must be maintained both at significant heating and at low temperatures, even if the changes are very sharp. Additionally, such a valuable parameter as plasticity should be mentioned - the decorative layer should stretch after the heating base, and not split. The lack of the necessary properties also guarantees the appearance of cracks after drying.

Heat resistant metalwork paints can be applied to any type of ferrous metal or alloy. The existing classification subdivides the coloring materials according to various criteria. First of all, the way of packaging. Sprays, cans, buckets and barrels are used as containers. Another gradation is made by dyeing methods, which determine the amount of paint consumed.

In everyday life, heat-resistant coloring compounds are applied to metal structures in baths, saunas, and to chambers for drying wood. They cover stoves and barbecues, fireplaces, radiators, mufflers and car brakes.

In practice, the decorative properties of the paintwork are of no small importance. In most cases, consumers are offered gray and black silver varieties. Other paints are much less common, although you can use red, white and even green paint if necessary. The assortment of leading manufacturers includes matte and glossy coatings of each specific shade.

Dyes in cans are relatively inexpensive compared to aerosols. Aerosol, at a seemingly low cost, is actually consumed very intensively.

If you want to paint the brake drums of a car, then at best you will have to use one spray can for two of them. In addition, there is a great risk of other auto parts clogging up with paint, they must be thoroughly covered during operation. Drying time in most cases does not exceed two hours.

With the help of alkyd and acrylic dyes, they decorate the components of heating systems - they will be able to transfer heating up to 100 degrees. The payment per kilogram of the train ranges from 2.5 to 5.5 thousand rubles.

Using epoxy mixtures, structures can be paintedthat heat up to a maximum of 200 degrees. Some of these paints do not require preliminary priming. The price range is much greater - from 2 to 8 thousand. The container capacity and the manufacturer's brand affect the price tag.

If you need paints for grilling or barbecues, you need to use ethyl silicate and epoxy ester paints. Then the permissible heating temperature will be 400 degrees. Using a one-component silicone compound, you can protect the metal from heating up to 650 degrees; the basis for the mixture is a polymer silicone resin, occasionally mixed with aluminum powder.

When heat-resistant glass and composites are added to the paint, it can withstand temperatures up to 1000 degrees. It should be noted that the cheapest compositions can be used for apartment radiators, because they do not heat up to more than 100 degrees. But metal stoves in private homes are regularly heated eight times stronger. The higher the permissible heating bar, the more expensive the dye mixture is. In terms of environmental and sanitary safety, water-based preparations are in the lead.

Additionally, you need to find out whether a particular paint is suitable for exterior or interior work. Glossy and light dyes warm up worse and give off heat to the outside for a longer period than dark ones. This is very important if you are going to paint stoves, heating systems.

Correct application of fire protection products is critical to their full function. Metal surfaces must be completely clean and free of all corrosion. The slightest deposits of oils and mineral crusts are unacceptable. Additionally, all dust is removed, metal surfaces are degreased. It is unacceptable to put fire-retardant paint without a preliminary primer, which must definitely dry to the end.

The composition is thoroughly mixed before use with a construction mixer, is left for about half an hour so that air comes out of it. The best flame retardant painting method is vacuum spraying, and if the surface area is small, a brush can be dispensed with.

On average, the consumption of fire retardant paint is from 1.5 to 2.5 kg per 1 sq. m. It is important to understand that these indicators are determined by the thickness of the coating, the application option and the density of the composition. The minimum amount of paint is two coats, and in most cases there are 3-5 coats.

When the structure is in plain view, it can be covered with a decorative layer over the protective compound. The surface must be prepared as carefully as possible, strictly adhering to the staining scheme and temperature regime prescribed by the manufacturer. Make a clear distinction between heat-resistant and heat-resistant paints. The latter compositions are suitable only for the design of the most heated parts.

If you decide to paint your car calipers, don't remove them - it's a waste of time and the risk of ruining your brakes. First, the wheels are removed, then the parts are cleaned of plaque and rust, only then they are painted in two layers.

When preparing to coat a metal oven, always read the manufacturer's instructions for the preparation. Some of the formulations can only be applied after careful preparation. When there are no special indications in this regard, you need to start by cleaning the surface from all traces of previous coatings - oil, deposits and dirt.

You need to remove rust with sandpaper, a drill with a special nozzle or a chemical rust converter. After removing even the smallest stains, the top layer must be washed and dried.

The oven must be degreased with a solvent such as xylene or solvent.

Exposure after such processing before staining is:

• on the street - 6 hours;
• in a room or technical room - 24 hours.

The ovens are necessarily painted with several layers of paint, which are applied in different directions, each after the previous one has dried.

Always find out how wide is the temperature range at which the paint can be used. In most cases, you can paint in the range from -5 to +40 degrees. But some modifications have more extensive capabilities, you should definitely know about them.

For information on how to paint the exhaust system with heat-resistant paint, see the next video.