RU2335580C1 - Inhibitor of amphoteric metal corrosion in alkaline media - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be applied in caustic etching and degreasing of aluminium, zinc and tin, as well as in galvanic elements with alkaline electrolyte for self-discharge inhibition of aluminium anodes. Inhibitor includes, wt %: ethyleneglykol 92-99, glutathione 8-1.

EFFECT: increased corrosion resistance of amphoteric metals.

2 tbl

Description

The invention relates to the field of protection of amphoteric metals in alkaline solutions using inhibitors and can be used for etching and degreasing metal surfaces before applying galvanic, chemical, conversion coatings, as well as in the production of chemical current sources to suppress self-discharge caused by corrosion of anodes in an alkaline electrolyte.

It is known to use sulfite-cellulose liquors to inhibit corrosion of aluminum in alkaline solutions as an inhibitor with a degree of protection of 99% (in a 0.1 M sodium hydroxide solution), 39.1% (in a 0.5 M NaOH solution), 30.8% (in a 1.0 M NaOH solution) [Altsybeeva A.I., Levin S.Z. Metal corrosion inhibitors. - L .: Chemistry, 1968, p.87]. From the above results, it can be concluded that it is not advisable to use a known inhibitor for pickling and degreasing aluminum, where the alkali concentration is 2-3 times higher (compared with a 0.1 M solution) because of the low degree of protection. For zinc and tin, the protection efficiency at the same NaOH concentrations is even lower.

The closest to the proposed inhibitor in terms of technical nature and the results obtained is the known inhibitor of traganate, which has a degree of protection of 82-87% for aluminum (in a 0.3 N NaOH solution) [ibid, p. 86]. For tin and zinc, the degree of protection is noticeably lower.

When developing the present invention, the task was to create such a corrosion inhibitor, which, firstly, would protect not only aluminum, but also other metals in alkaline media and, secondly, would provide more effective protection against corrosion of aluminum and other metals. To achieve the technical task, it was proposed to use a combination of two products - ethylene glycol (playing the role of macroadditives) and glutathione (acting as a microadditive). It was assumed that both substances, when combined in an alkaline solution, will significantly enhance each other's action, i.e. show synergistic interaction.

Ethylene glycol is a dihydric alcohol, glutathione tripeptide. The composition of the proposed inhibitor components are in the following concentrations, wt.%:

ethylene glycol 92-99 glutathione 8-1.

The inhibitor is introduced into a solution of alkali (NaOH) at a concentration of 6-11 g / l. The corrosion rate of metals in an alkaline solution was measured for aluminum by volumetric (by volume of hydrogen) and gravimetric (by loss of sample mass) methods, for zinc and tin - only the latter. The protective anticorrosive effect of the inhibitor is shown in table 1. For a known inhibitor, the data are collected in table 2.

As follows from the above results, the proposed inhibitor protects Al, Zn and Sn much more effectively than the known one.

For etching and degreasing of aluminum, zinc and tin, when NaOH solutions are used in concentrations of not more than 0.25-0.5 M, Al protection exceeds 96% (at the optimal concentration of components). At the same time, a known inhibitor provides protection of only 90% or less. A similar pattern is observed for zinc and tin. It should be especially noted that at alkali concentrations of 1-2 M, which can already be used in galvanic cells with an aluminum anode, the degree of protection at the optimum concentration of inhibitor components remains above 96%, which ensures a sufficiently low self-discharge value of the chemical current source.

Thus, the developed inhibitor can be used for etching and degreasing of Al, Zn and Sn, as well as in a galvanic cell with an alkaline electrolyte and an aluminum anode.

Table 1
The degree of corrosion protection of the proposed inhibitor (10 g / l) №№ Metal Concentration, mol / L t, ° C Mac.% Degree of protection, % ethylene glycol glutathione one 2 3 four 5 6 7 one Al 0.25 twenty 99 one 93.3 2 - // - - // - - // - 95 5 97.5 3 - // - - // - - // - 92 8 99,2 four - // - 0.25 40 99 one 90.1 5 - // - - // - - // - 95 5 94.5 6 - // - - // - - // - 92 8 96.1 7 - // - 0.5 twenty 99 one 91.1 8 - // - - // - - // - 95 5 95.9 9 - // - - // - - // - 92 8 98.5 10 - // - 0.5 40 99 one 87.8 eleven - // - - // - - // - 95 5 89.2 12 - // - - // - - // - 92 8 92.9 13 - // - 1,0 twenty 99 one 90.2 fourteen - // - - // - - // - 95 5 93.3 fifteen - // - - // - - // - 92 8 97.3 16 - // - 2.0 - // - 99 one 85.8 17 - // - - // - - // - 95 5 92.0 eighteen - // - - // - - // - 92 8 96.3 19 Zn 0.25 twenty 99 one 94.4 twenty - // - - // - - // - 95 5 96.3 21 - // - - // - - // - 92 8 97.9 22 - // - 0.25 40 99 one 85.8 23 - // - - // - - // - 95 5 87.2 24 - // - - // - - // - 92 8 90.2 25 - // - 0.5 twenty 99 one 90.5 26 - // - - // - - // - 95 5 92.2 27 - // - - // - - // - 92 8 93.9 28 - // - 0.5 40 99 one 83.5 29th - // - - // - - // - 95 5 85,4 thirty - // - - // - - // - 92 8 87.0 31 - // - 1,0 twenty 99 one 75.9 32 - // - - // - - // - 95 5 79.9 33 - // - - // - - // - 92 8 85.8 34 - // - 2.0 - // - 99 one 73.3 35 - // - - // - - // - 95 5 78.6 36 - // - - // - - // - 92 8 83.7 37 Sn 0.25 twenty 99 one 71.5 38 - // - - // - - // - 95 5 73.9 39 - // - - // - - // - 92 8 77.1 40 - // - 0.25 40 99 one 69.2 41 - // - - // - - // - 95 5 70.7 42 - // - - // - - // - 92 8 73.5 43 - // - 0.5 twenty 99 one 70.5 44 - // - - // - - // - 95 5 72.5 45 - // - - // - - // - 92 8 73.9 46 - // - 0.5 40 99 one 67.3 47 - // - - // - - // - 95 5 69.9 48 - // - - // - - // - 92 8 71.9 49 - // - 1,0 twenty 99 one 73.3 fifty - // - - // - - // - 95 5 74.5 51 - // - - // - - // - 92 8 76.6 52 - // - 2.0 - // - 99 one 68.5 53 - // - - // - - // - 95 5 70.3 54 - // - - // - - // - 92 8 73.7

table 2 Degrees of corrosion protection with a known inhibitor (traganate, 10 g / l) №№ Metal t, ° C Degree of protection, % Conc. NaOH, mol / L one Al twenty 90.2 0.25 2 - // - 40 86.3 0.25 3 - // - twenty 81.3 0.5 four - // - 40 78.5 5 - // - twenty 71.1 1,0 6 - // - 40 65.8 2.0 7 Zn twenty 81.7 0.25 8 - // - 40 80.1 0.25 9 - // - twenty 77.3 0.5 10 - // - 40 79.2 1,0 eleven - // - twenty 80.5 2.0 12 Sn twenty 69.2 0.25 13 - // - 40 62.5 0.25 fourteen - // - twenty 59.6 0.5 fifteen - // - 40 57.0 1,0 16 - // - twenty 54,2 2.0

Claims (1)

Corrosion inhibitor of amphoteric metals in alkaline media, characterized in that it contains ethylene glycol and glutathione at the following concentrations of components, wt.%: ethylene glycol 92-99 glutathione 8-1