What have to be paints on metal?
At the metals applied in housing construction, two large shortcomings: vulnerability at influence of aggressive environment and quite limited color scale. That is why practically always, in 80 - 90% of cases, we see metals painted. Paint, and especially special paint, perfectly protects metal and decorates products from it.
This article - about paints on metal for the house. Paints for cars, special paints for chemical and foundry productions are another story altogether.
of Paint have to be beautiful
Simple truth - paint in order that the thing became beautiful.
The scale of the paints applied nowadays is not simply huge. The existing paints are capable of a lot of things. For example, to give to one metal a type of another, to improve metal or to artificially make old him.
The paints imitating effect of a patina are popular. Smooth transitions of one shade of paint to another effectively emphasize bends of a surface of metal products.
Such “decoration“ of metal is incomparable cheaper, than drawing other types of coverings, for example, of nickel plating, not to mention gilding. Besides, if necessary it is easy to remove and put a paint and varnish covering again.
of Paint have to protect from corrosion
Special anticorrosive paints reliably provide long protection of a metalwork against corrosion. Such paints are especially necessary for protection of designs with a difficult profile as it is more difficult to clear them.
Depending on structure anticorrosive paints and primers provide barrier protection, do metal passive in relation to hostile environment, or play a protector role.
Barrier protection means mechanical isolation of a surface of metal from hostile environment.
Some substances, usually borata, silicates, chromates, promote education on a surface of metals of a dense film of slightly soluble connections, i.e. passivate metal. Organic inhibitors are more effective.
Tire-tread protection of metal is that powders of metals include more active in composition of paint, than protected. Under the influence of hostile environment first of all additives are dissolved, and the protected metal does not collapse.
of Paint have to be thermo - and fire-resistantMetals carry well out by
heat therefore they are used everywhere for production of heating devices. However such products also need coloring. But not any paint is steady against action of high temperatures.
Surfaces, the heated not above 80 °C, it is possible to paint with any paints for metals, for example, usual alkidny or oil.
Batteries of steam heating heat up to 100 °C. For their coloring not the usual, and modified paints on the basis of alkyd and acrylic resins into which composition the special additives preventing yellowing of coverings are entered are necessary.
The temperature is higher, the requirements to paints in this connection also their structure changes become more tough. When heating to 120 °C it is expedient to use acrylic or epoxy paints and primers, and at 150 - polyurethane coverings. As not turning yellow pigments in them use phosphate of zinc or zinc dust.
Paints on a basis an epoxybottom - bituminous, ethylsilicate and epoxy-ether pitches maintain heating to 200, and even to 400 °C.
The most heat-resistant paints maintaining heating to 450 - 600 °C make on the basis of silicone pitches.
The majority of metals does not burn. But it is not necessary to identify combustibility with fire resistance. On fire resistance metal designs among building constructions of other types are nearly the worst. Insufficient fire resistance of a metalwork was one of the reasons of a building collapse of the World Trade Center.
Fire resistance of a metalwork can be increased significantly, having applied a fireproof covering on a metal surface.
Everything materials for fire protection of a metalwork can be divided into two groups:
- the isolating not distending materials operating thanks to low heat conductivity;
- the distending materials changing under the influence of high temperature.
Not distending paints when heating absorb heat due to decomposition, releases of inhibitory gases or release of water.
In usual service conditions the distending coverings carry out protectively - decorative functions. However under the influence of fire the covering distends, chars and turns into the porous heat-insulating coke which protects metal from heating and at the same time interferes with distribution of a flame. Thickness of a protective layer at the same time increases by 10 - 50 times. I.e. it is enough to put a fireproof layer only 1 mm thick that it at the fire turned into the isolating layer thickness in several centimeters.
The distending paints provide fire resistance within 45 - 90 minutes.