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

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 dimethylbenzylamine 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): CO 2 (0.2-0.6 vol.%), NH 3 (20-60 mg/m 3 ) and H 2 S (10-30 mg/m 3 ), either separately or in combination.In an uninhibited atmosphere with 0.6 vol.% CO 2 + 60 mg/m 3 NH 3 (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 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 CO 2 (0.6 vol.%) + H 2 S (30 mg/m 3 ) or H 2 S (30 mg/m 3 ) + NH 3 (60 mg/m 3 ) 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 (CO 2 + H 2 S).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 (NH 4 ) 2 S or (NH 4 ) 2 CO 3 salts as reaction products of H 2 S or H 2 CO 3 with NH 3 in the solution, which occurs in the surface phase film of moisture. At the same time, this Int. J. Corros. Scale Inhib., 2018, 7, no. 3, 331-339 332 volatile corrosion inhibitor completely prevents local damage to brass and copper under all conditions studied.

Suppression of local corrosion of steel, brass and copper with IFKhAN-114 volatile inhibitor

“…It was shown earlier in a number of works [1][2][3] that volatile corrosion inhibitors (VCI) of IFKhAN series efficiently suppress the atmospheric corrosion of steel [1][2][3], brass [3] and copper [3] under conditions of 100% relative humidity at the background and multiply increased concentrations of corrosion stimulants (CSs) NH 3 , H 2 S and CO 2 . Simultaneous presence of any two CSs reduces the effectiveness of some representatives of this series (IFKhAN-118 [2,3]) with respect to the rate of general corrosion and practically does not change that of other ones (IFKhAN-114 [2,3]). The presence of all three CSs increases the efficiency of VCI in a number of cases.…”

“…The presence of all three CSs increases the efficiency of VCI in a number of cases. However, the presence of all these corrosion stimulants separately or together, as a rule, causes significant local damage to the surface of metals [2,3]. Ulcers and numerous pits are formed on the surface of steel (St3), biphasic (α+β) brass and copper in 10-day tests.…”