Protection of metals in neutral environments with pH 5–9 (in humid atmospheres and various aqueous solutions) can be achieved by forming thin coatings (up to several tens of nm) on their surfaces due to adsorption and more complex chemical interaction of organic corrosion inhibitors with the protected metal. This brief review discusses the features of the formation and protection of metals in the vapor-gas phase, i.e. volatile corrosion inhibitors (VCI) mainly on iron and carbon steels, copper and zinc. The important role of VCI chemisorption and, as a consequence, the possibility of its relatively long protective aftereffect under harsh conditions of high air humidity and periodic moisture condensation on the surface of metals is shown. A method has been demonstrated for increasing the efficiency of metal protection through the combined use of VCI and volatile silanes, including their layer-by-layer adsorption on the protected metal. The ability of silanes to undergo chemical transformations when interacting with water vapor turned out to be useful for the purposeful creation of protective nanoscale coatings on metals from the vapor-gas phase on metal surfaces with delayed VCI desorption, i.e., a relatively long protective aftereffect

The results of field tests of the effectiveness of a mixed chamber inhibitor (a mixture of octadecylamine and benzotriazole) for the protection of metals in the tropics are presented. It is shown that the chamber treatment of metals with this mixture with the packaging of processed samples in plastic bags:
– provides full protection of copper, brass and galvanized steel in humid, marine and coastal tropical climates for up to 9 months;
– provides full protection of steel in humid and coastal tropical climates for up to 9 months and in marine tropical climates for up to 3 months.

The possibility of obtaining a coating with multimodal roughness on low-carbon steel by thermal oxidation in nitrate-phosphate solution as the first step in the formation of a superhydrophobic surface was shown. To determine the coating with optimal characteristics we varied the solution composition, temperature and oxidation time. The phase composition of the obtained coating was studied. Ethanol solution of stearic acid was used as a hydrophobizing agent. It was shown that the formed superhydrophobic surface is comparable in its characteristics with the coating obtained after laser burning and has good protective properties

For applying a painting system on the surface of aluminum alloys, special primers are formed, including the method of chemical oxidation. Primers should serve as adhesion promoters and provide additional anti-corrosion protection. In the present work, ultrathin conversion primer coatings were obtained in the environmentally friendly IFKhANAL-2M converting composition based on molybdates and phosphates. To improve the protective and adhesive properties of the coatings, they were modified by changing the converting composition and subsequent filling of the coatings in a corrosion inhibitor solution. Among the studied modifying additives, 1,2,3– benzotriazole (BTA) showed the best result. Coatings obtained in a solution with the addition of BTA effectively adsorb the corrosion inhibitor at the stage of coating filling, show good protective properties during corrosion tests in a humidity chamber and high adhesion parameters of painting system. In terms of these properties, they are close to traditional primers obtained in chromate conversion compositions.

Chamber protection is a promising and rapidly developing method of vapor-phase protection of metals from atmospheric corrosion by inhibitors. Corrosion screening of individual organic inhibitors has shown that chamber treatment (CT) with 2-ethylhexanoic acid (EHA) efficiently inhibits the initiation of zinc corrosion.
A set of accelerated corrosion, electrochemical and physical methods was used to study the specific features of zinc chamber protection and mechanisms of EHA action. It was shown that:
– as the temperature of zinc CT increases, the EHA efficiency first increases and then decreases. The growth of the protective effect is associated with an increase in the inhibitor’s vapor pressure that favors adsorption. The descending branch of the temperature dependence is due to a decrease in adsorption as the adsorbent (zinc) is heated. The optimal temperature of zinc CT with EHA is 100°C.
– the efficiency of EHA increases as the CT time is increased to 1 hour. This is the optimal duration for this system. Longer CT does not provide a positive effect and is inexpedient.
– CT of zinc under the optimal conditions results in the formation of surface adsorption films of EHA up to 100 nm thick. The acid reacts with the metal and the surface oxide to form the C4H9-CH(C2H5)-COO-Zn-OH basic salt. Once zinc is removed from the chamber and exposed to open air, the basic salt is dehydrated and converted to a compound with the formula CH(C2H5)-COO-Zn-O-Zn-OOC-СН(C2H5)-C4H9 that is responsible for metal protection. This process determines the growth in the protection efficiency during the first day of metal exposure outside the chamber at room temperature.
– the surface layers formed on zinc during CT followed by exposure to air passivate the metal and stabilize its passive state. Their action is associated with both shielding of the surface from the corrosive environment and inhibition of corrosion processes on the active metal surface. The EHA efficiency in zinc protection was confirmed by field tests.

Methods for preliminary modification of the surface of structural metals with compositions based on organosilanes have been developed. The compositions consisted of solutions of both individual organosilanes and two–component mixtures consisting of two organosilanes or an organosilane and an organic corrosion inhibitor. As a result of this modification, a self– assembled siloxane polymeric/oligomeric nanoscale layer is formed on the metal surface, which is capable of changing the physicochemical properties of the metal surface, in particular, reducing the tendency of the metal to corrosion destruction. This paper presents the results of one–year full–scale corrosion tests of structural metals: steel, copper, zinc, the surface of which is modified with compositions based on organosilanes. It is shown that the preliminary modification of the surface of metals by these compositions leads to inhibition of both uniform and local corrosion of metals. The greatest inhibitory effect was demonstrated by two– component modifying compositions: mixtures of vinyl- and aminosilane, vinylsilane and benzotriazole. The mechanism of corrosion inhibition by layers formed as a result of surface modification with two–component mixtures is considered

Evolution of electrochemical properties of multilayer polymer composite coatings and their constituent primer and inert insulating layers on various metal substrates in chloride media are considered.
It is shown that electrochemical models for typical functional coating layers (insulating and priming) can undergo significant changes during exposure in aggressive environments. The smallest changes are observed for an insulating layer with an inert polymer base and with inert fillers deposited on an inert (Pt) substrate: the digital model is described by the simplest equivalent circuit (ES) with one characteristic relaxation process over the entire exposure time range.
For the same coating on a corroding steel substrate, such a model is correct only at the initial stage of exposure. Later, as the under film corrosion develops, the ES evolves into a system with two relaxation processes. In primer coatings with a corrosive metal filler (Zn), the situation becomes more complicated and two relaxation processes are recorded from the initial exposure period.
For multilayer composite coatings containing spatially separated layers with active and inert fillers, three characteristic relaxation times are identified on a corroding steel substrate. This is in accordance with the model of multiphase layered bulk-filled polymer composites and justifies the use of additive Voit ES.
Digital models of the evolution of electrochemical properties for all the studied systems were proposed, including inert layers on steel and platinum, thin and multilayer Zn–filled primer layers and multilayer coatings of the listed materials at different temperatures in chloride media. The obtained results also allow us to propose a method of non-destructive EIS control of physico-chemical and corrosion processes in composite polymer protective coatings at different stages of exposure in aggressive environments.