The operation of metal structures and parts is often accompanied by exposure to aggressive environments. Examples include automobile bodies and roofing with fences and all kinds of frame cladding. It is not always necessary to correct emerging defects by welding or straightening tools, but filling with a primer mixture may well justify itself. And best of all, metal putty with an extensive range of protective effects can handle this operation.
Purpose of coverage
Putty has a protective and restorative effect on metal surfaces. In practice, it is used as an intermediate layer between the directly structure of the workpiece and the external decorative coating. In a way, this is a preparatory base for ordinary paint, but designed for increased protection of the base material. For example, heat-resistant putty for metal is able to reflect thermal effects at a temperature of -50 ... + 120 ° C, while maintaining the primary mechanical properties. Depending on the modification, this product can provide protection against corrosion, aggressive alkalis, gasoline, weathering and direct contact with water. Therefore, there are special formulations oriented to operation in an industrial environment, in the open air, indoors, at electric power enterprises, etc.
Material Composition
A large proportion of almost any putty of this type falls on epoxy. The remaining parts are various kinds of pigments and modifying additives with plasticizers. For this reason, the coefficient of non-volatile elements is about 90%. The specific set of minor putty components for metal depends on the application. It can be both neutral substances for filling defects, and reinforcing fibers like fiberglass inclusions that improve the physical properties of strength. Sometimes additional elements are added already in the process of preparing the solution. These include chalk or kaolin, which contribute to the rapid hardening and drying of the mixture.
Varieties of coverage
Of fundamental importance for the technical and operational qualities of the putty is the type of filler used. According to this parameter, the following types of the main component are distinguished:
- Fine-grained filler. Provides the effect of delicate alignment, masking microscopic pores and forming a flat surface. This is the optimal putty for metal for cars, which can be used as a topcoat.
- Lightweight base. It’s also a kind of fine-grained putty, but without a decorative effect. Suitable for working with small scratches, chips and cracks. A distinctive feature of this composition can be called a modest mass, almost without affecting the structural characteristics of the workpieces.
- Coarse filler. In this case, the emphasis is not on leveling or preparing the surface for the final finish, but on a rough correction of serious defects on the surface. In essence, this is a primer, after which grinding is performed. Coarse putties are characterized by high strength and overall mechanical stability.
- Reinforcing base. Even more wear-resistant composition, due to which large damage with through holes is eliminated. Just in such compositions contains fiberglass and metal powder.
Surface preparation for applying putty
The working conditions and requirements for the target surface may be different depending on the characteristics of a particular composition. For example, before there was a separation between the primer and the putty itself, which was applied after the sealing of the defects. Today, the question of in what sequence and how the putty is laid, on the ground or on metal, is not worth it. There is only one rule - a directly damaged surface, in order to strengthen and protect it, can be processed directly with any compound containing epoxy resin. A special and separate primer with other mixtures is not required. Another thing is that the surface should be as clean as possible from traces of corrosion, scale, burnouts and dirt with oil stains.
Cooking composition
The base for putty is supplied in the form of a dry mixture with a volume of 0.25 to 60 kg. Initially, you should expect a flow rate of approximately 600-700 g / m 2 with a standard thickness of up to 1 mm. If you plan to use a pneumatic spray gun in your work, then the consumption will be even lower - approximately 200-300 g / m 2 , taking into account that the coating thickness is halved. In this ratio, putty is prepared for metal for painting for cars. The dry mixture consists of two components, one of which is a base, and the second is a hardener. First, the base is mixed with water using a construction drill-mixer at low speeds. Next, a hardener is introduced and, in the same mode, stirring is performed for 10 minutes until a homogeneous mass is formed.
Coating
After standing the finished mixture for 20-30 minutes, they begin to work. Laying can be done with a pneumatic sprayer, with a traditional tool in the form of a spatula, and with a complete tube with a small nozzle, if we are talking about a small processing area. Putting putty on bare metal is carried out by identical layers over the entire area and is immediately leveled. To distribute the mass over the entire area, it is worth using the plaster rule. Also, do not forget that the mixture, due to the characteristics of the formulation, does not retain plasticity for a long time, so the operation should be performed as soon as possible. According to the instructions, the viability of mixed putty when applied with a spatula is 1-1.5 hours, and when working with a spray gun - up to 6 hours. After polymerization, the laid and distributed coating is sanded with fine abrasives. To do this, it is advisable to use a grinder with a felt wheel. Then you can proceed to decorative paintwork.
What to consider when using the material?
Experts advise in advance to focus on favorable environmental conditions. It is best to perform work at a humidity of not more than 80% and a temperature of at least +5 ° C. If the material after preparation turned out to be too viscous and causes problems during application (especially for spray guns), then it is worth using special solvents for puttying on metal - using the grades P-4 and P-5A. Do not forget about the chemically active substances in the putty. Throughout the entire workflow, it will not be out of place to use personal protective equipment.
Conclusion
The protection functions of metal surfaces from all sorts of threats have long been adopted by coatings. They protect the material from light mechanical influences and from corrosive processes. But under the conditions of operation of the material in aggressive environments and taking into account the existing damage, the optimal solution would be to use putty on metal, which has a repair and restoration effect. Its main advantage is that it prevents existing lesions from continuing to destroy the structure from the inside. In addition, the protective properties of many epoxy primers are superior to alternative coatings in effectiveness.