Protective ability of volatile inhibitors of IFKhAN series in atmospheric corrosion of brass and copper at high concentrations of CO2, NH3 and H2S in air

• V.I. Vigdorovich^1,2, L.E. Tsygankova³, A.N. Dorohova³, A.V. Dorohov¹, L.G. Knyazeva¹ and A.A. Uryadnikov³

¹ All-Russian Scientific Research Institute of Use of Machinery and Oil Products, Novo-Rubezhnyi per., 28, Tambov, 392022, Russian Federation
² Tambov State Technical University, Sovetskaya str., 106, Tambov, 392000, Russian Federation
³ Derzhavin State University, ul. Internatsyonalnaya str., 33, Tambov, 392000, Russian Federation

Abstract: The protective efficacy of volatile inhibitors (VCI) IFKhAN-8 (an amino alcohol), IFHAN-112 (a mixture inhibitor based on benzotriazole), IFKhAN-114 (a non-equimolar mixture of a polyamine and a weak organic acid) and IFKhAN-118 (a dimethyl¬benzylamine salt) was studied in atmospheric corrosion of M2 copper (99.7 wt.%) and L62 two-phase brass (22.5 wt.% Zn and 67.7 wt% Cu) in the presence of corrosion stimulators (CS): CO2 (0.2–0.6 vol.%), NH3 (20–60 mg/m3) and H2S (10–30 mg/m3), either separately or in combination. In an uninhibited atmosphere with 0.6 vol.% CO2 + 60 mg/m3 NH3 (three times higher than the normally permissible CS concentrations) with a relative humidity of 100%, corrosion of copper and brass has a pronounced local character. In addition, there is a darkening of a significant fraction of the surface of metals (CuO film). The protective efficiency (Z%) of IFKhAN-112, IFKhAN-114, and IFKhAN-118 in relation to the total corrosion is 75% (brass) and 85% (Cu); 82% (brass) and 79% (Cu) and 89% (brass) and 85% (Cu), respectively. In the atmosphere with CO2 (0.6 vol.%) + H2S (30 mg/m3) or H2S (30 mg/m3) + NH3 (60 mg/m3) in the presence of IFKhAN-114, Z is 75% (brass, copper). With the other inhibitors being studied in the atmosphere, Z is reduced to 13% or even stimulation of corrosion is observed (CO2 + H2S). In the presence of all the three corrosion stimulators, IFHAN-114 with a protective effect of 96% (brass) and 95% (copper) is again the most effective. This VCI hinders the anodic reaction of ionization of the metals both at the initial stage of exposure in the medium and after 96 hours of exposure. IFHAN-114 inhibits the anodic process in the presence of (NH4)2S or (NH4)2CO3 salts as reaction products of H2S or H2CO3 with NH3 in the solution, which occurs in the surface phase film of moisture. At the same time, this volatile corrosion inhibitor completely prevents local damage to brass and copper under all conditions studied.

Keywords: copper, brass, corrosion, hydrogen sulphide, carbon dioxide, ammonia, volatile inhibitors, protection

Int. J. Corros. Scale Inhib., 2018, 7, no. 3, 331-339 PDF (501 K)
doi: 10.17675/2305-6894-2018-7-3-4

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