Volatile inhibitors of atmospheric corrosion of ferrous and nonferrous metals. V. Study of the adsorption of inhibitors on steel from an aqueous electrolyte solution

Abstract

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

Carbon nanocomposites in the corrosion inhibition

“…In this work, two inhibitors of different chemical composition were selected as corrosion inhibitors. Inhibitor VNH-L-113 (1-morpholinomethylcyclohexylamine), belongs to Schiff bases, which are known as corrosion inhibitors in neutral [7] and acidic [8] media. Inhibitor SNPKh-1004 is often used in the practice of corrosion protection in the oil and gas industry [9].…”

The protective effect of Schiff and Mannich bases on steel corrosion in neutral media

“…It was previously shown that the limiting stage of anodic dissolution is the incorporation of metal ions into the structure of the near-electrode layer of water molecules [5]. When organic inhibitors are added to the electrolyte, they are adsorbed at the metal -electrolyte interface [6], which leads to a decrease in the double layer capacitance due to a decrease in the dielectric constant. As a result, iron ions formed during anodic dissolution, are introduced into the medium with a dielectric constant lower than water, which leads to an increase in the activation energy of the electrochemical reaction of anodic dissolution [7]:…”

Volatile corrosion inhibitors for ferrous and non-ferrous metals and alloys: A review

“…Variation of vapour pressure (p 0 ) with latent heat of sublimation for DICHAN, cyclohexylamine benzoate and di-isopropylamine nitrile are presented in Figure 1 [46,47,53]. Altsybeeva et al [54,55] studied the action mechanism of volatile inhibitors having different vapour pressure but did not get any regular trend. Further, it was also discussed about the kinetics of VCIs from the surface of various metals, action mechanism and higher inhibition efficiency upon electrostatic application.…”

“…The trend and technology has allowed new methods for a range of VCI applications to be reliably extended into new areas of applications. The corrosion protection in oil & gas, military, automotive, electronic, electrical, and other industrial sectors see existing and new technologies which increase efficiency and service life and decrease the total cost [74][75][76].…”