Oil and gas sector
In the oil and gas sector, the problem of corrosion protection is very acute. In mines and drilling tunnels, corrosion of steel can reach enormous proportions - up to 3 mm of corrosion per year. The protective coating must resist corrosive factors such as aggressive environments, bacteria and mechanical wear. Internal and external pipe coatings are mainly divided into epoxy, phenolic, epoxy-phenolic, novolac, nylon, urethane and polyethylene depending on the chemical composition.
There are some specialized techniques for applying protective coatings. For example, some companies use the following application methods: high-speed, electric arc metallization, plasma, gas plasma spraying and plasma surfacing. These technologies allow the application of iron-based stainless alloys, nickel-based alloys, hard alloys, stainless steels, zinc, aluminum and their alloys as coatings. They provide high adhesion strength of the coating with the coated surface, but at the same time they are technically complicated and very expensive.
For example, Tatneft produces several types of oilfield equipment with protective coating. Firstly, metal-plastic pipes (MPT). Their advantages include resistance to aggressive media, as well as reduction of salt and ARPD deposits, while their disadvantages include high requirements to surface preparation, low temperature resistance, difficulty of surface application and high cost. Secondly, steel pipes with polymer outer insulation and internal cement-sand coating. Their advantages are similar to those of MPT, the disadvantages are a high degree of dependence of the strength and durability of the coating on the quality of the applied composition and application technology, technical complexity of application on the surface and high cost. The third type of products - steel pipes with silicate-enamel coating. Among their advantages - resistance to aggressive media, ability to reduce salt deposits and ARPD, a significant range of operating temperature - from -60 to +350°C, high resistance to abrasive wear. The disadvantages are similar to those listed for pipes with polymer outer insulation and internal cement-sand coating. And, finally, tubing with protective polymer coating, for application of which PEP-585 material is used on the surface. Polymer-coated tubing is characterized by resistance to aggressive media, reduction of salt and ARPD deposits and hydraulic resistance. The disadvantages are similar to those listed above.
If the pipe coating must withstand elevated temperatures, ESP working bodies with a protective coating of polyphenylene sulfide (PPS) are produced. The technology consists of applying a cross-linking agent in the form of a primer with the function of corrosion protection between the base metal and the protective polymer coating after surface cleaning. The advantages of the technology include resistance to aggressive media and the ability to reduce salt deposits, while the disadvantages include the relatively high cost and relative short life of the coating.
But if pipes and equipment are not exposed to elevated temperatures (more than 80 degrees Celsius), the optimal price/quality is polyethylene coatings, applied from the outside by gas-flame method, and if from the inside - by rotary rotation.
The coatings formed by such methods:- are easy to apply, can be applied directly on site (subject to fire regulations);
- have an absolute anti-osmotic coating (i.e. water molecules and other liquids cannot penetrate through the coating);
- resist the development of bacteria and the formation of mineral-calcium deposits;
- have high abrasion resistance (it is problematic to remove this coating from the surface by sandblasting).
If the coating requires strengthening of some properties, then applying the same method of gas-flame application and another material we get:- increased wear resistance (materials based on supermolecular polyethylene (exp. up to 100 g.) and materials based on polyamide (exp. up to 150 g.);
- wear resistance, chemical resistance and heat resistance (Teflons, exp. up to 200 g).