The paper discusses the relationship between the physicochemical and electronic characteristics of various metals and molecular parameters of inhibitors that allows a better prediction of the efficiency of volatile inhibitors of atmospheric corrosion (VIACs) of ferrous and nonferrous metals. The high efficiency of commercial VNKh-L inhibitors based on Schiff and Mannich bases as VIACs is substantiated. It is demonstrated by analyzing the main molecular characteristics that products of complex condensation of nitrogen-containing compounds with aldehydes can serve as highly efficient VIACs. Key words: physical and chemical aspects; volatile inhibitors; atmospheric corrosion; ferrous and nonferrous metals; Schiff and Mannich bases.Received: August 10, 2012August 10, . doi: 10.17675/2305August 10, -6894-2012 According to the current concepts adopted by most researchers [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16], the efficiency of a volatile inhibitor of atmospheric corrosion (VIAC) generally depends on the pressure of its saturated vapor (P 0 ) at a given temperature, the diffusivity (D) determined by the molecular mass, and the minimum protective concentration (C min ) in water with respect to a metal to be protected. The first two factors, unlike the third one, are independent of the metal nature. The minimum protective concentration depends on the properties of an inhibitor as well as on the metal nature. The mere existence of such a term as "radius of VIAC protective action" can prove that diffusion of an inhibitor across the air layer from the surface of evaporation to the surface of a water film on the metal is the slowest step [7]. Otherwise, the efficiency of VIAC would be independent of the thickness of the air layer [9][10][11][12][13].A detailed analysis of the plot of the efficiency of VIAC vs. D and P 0 , which has been performed for inhibitors used to preserve metallic parts in the last 40-50 years [1, 9-13, 15, 17], revealed that the vapor pressure of a "perfect" VIAC should range from 1·10 -6 to

Criteria for selection of inhibitors based on their metal corrosion inhibition factors in an environmental chamber have been proposed. It has been demonstrated that a wide range of ferrous and nonferrous metals are efficiently protected by 1-(morpholino)(phenyl)methylbenzotriazole conventionally named as VNKh-L-408. The basics of its production and application technology have been developed. In [1], we have demonstrated that thermally stable molecular compounds such as Schiff and Mannich bases are promising as volatile inhibitors of atmospheric corrosion (VIACs) of ferrous and nonferrous metals. When choosing an inhibitor that can be recommended for development of the commercial production technology, we considered the range of metals protected by the inhibitor and fast protection for dissimilar metals achievable by such inhibitor. Accelerated corrosion tests are carried out under the assumption that the atmospheric corrosion of metals follows the same mechanism, whether under natural conditions or in an environmental chamber. In the latter case, several cycles are usually required to initiate corrosion. The degree of corrosion depends on the resistance of the metal to atmospheric corrosion, provided that the test duration is the same.According to GOST (State Standard) 9.509 [2], it is nearly always required to choose a proper test cycle (for a specified testing method) from test results for some protective agent with a known protection period certified by industrial testing. The proper test cycle in an environmental chamber was determined from the protection periods of the NDA and KhTsA inhibitors specified in GOST 9.014 [3]. One test cycle corresponds to ~3.5-4 months of storage in an unheated warehouse or under a shed in an industrial coastal town.Because dissimilar metals differently corrode in air in the absence of inhibitors, it is advisable to assess the efficiency of an inhibitor from the inhibition factors of metal

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Adsorption of ten Mannich and Schiff bases on steel from a mixed electrolyte solution (30 mg/dm 3 NaCl + 50 mg/dm 3 Na 2 SO 4 ) was studied. The adsorption isotherms show linear segments in the medium coverage range, which may be equally attributed to both the Frumkin and Temkin isotherms. Unfortunately, experimental data are insufficient to distinguish among them. It was demonstrated that the mechanism of action of the inhibitors in vapor phase differs from that in a model electrolyte solution and that testing of volatile inhibitors in electrolytes provides no accurate pattern of corrosion inhibition in the vapor phase. The VNKh-L-21 and VNKh-L-408 inhibitors form nanoclusters that merge on the surface into a polymolecular adsorption layer. Key words: Schiff and Mannich bases, adsorption, mixed electrolyte, electrode surface coverage, blocking effect, Frumkin and Temkin isotherms, nanoclusters.Received: August 10, 2013August 10, . doi: 10.17675/2305August 10, -6894-2013 Experimental Electrochemical studies on the adsorption of inhibitors on steel were carried out in a mixed electrolyte (30 mg/dm 3 NaCl + 50 mg/dm 3 Na 2 SO 4 ), which is believed to simulate the electrolyte that is condensed on metal surfaces under atmospheric corrosion conditions at 100% relative humidity [1,2]. The adsorption was studied by measuring the differential capacitance of the double electrical layer (DEL) with an R-5021 AC bridge [3].Measurements were carried out with parallel connection of a capacitor and a resistor. The alternating current frequency was 1 kHz. Since Faraday processes and pseudocapacitance cannot be eliminated completely, one should keep in mind that the measured capacitances give only a rough measure of the DEL capacitance and therefore the calculation will provide some affective surface coverage of an electrode with an inhibitor.A rod shaped St3 electrode with a surface area of 1 cm 2 was prepared according to a conventional procedure for electrochemical studies. It was found during the preparation and optimization of the experimental conditions that the most reproducible results were