JPS58224187A - Corrosion preventive lithium bromide composition - Google Patents

Abstract

PURPOSE:To provide a corrosion preventive compsn. which suppresses effectively the corrosiveness to metal of an aq. LiBr soln. contg. LiOH to be used particularly for an absorption type refrigerator, etc. by consisting the same of said aq. soln., alkali metallic salt of molybdic acid and alkali metallic salt of nitric acid or nitrous acid. CONSTITUTION:A corrosion preventive LiBr compsn. is produced by adding 0.001-0.05wt% alkali metallic salt of molybdic acid, 0.01-0.1wt% alkali metallic salt of nitric acid or 0.01-0.05wt% alkali metallic salt of nitrous acid to an aq. LiBr soln. contg. LiOH (an aq. soln. A). The aq. soln. A constituting said compsn. is prepd. by adding LiOH to 53-55wt% an aq. LiBr soln. which is normally used and regulating the concn. of LiOH to 0.01-0.3wt%. Na salt and Ka salt are easy to use and are preferable as the alkali metallic salt of nitric acid or nitrous acid. There are mild steel, copper, brass, etc. as the metallic material to be prevented of corrosion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an additive that effectively inhibits metal corrosion of lithium bromide aqueous solution compositions containing lithium hydroxide, particularly lithium bromide aqueous solutions containing lithium hydroxide used in absorption refrigerators, etc. and a lithium bromide aqueous solution containing lithium hydroxide.

It is well known that lithium bromide aqueous solution is corrosive to mild steel, copper, brass, etc., and when these metal materials are used in absorption refrigerators and lithium bromide aqueous solution is used as the absorption liquid, Various types of corrosion inhibitors have been proposed, some of which are in actual use.

For example, nitrates such as lithium molybdate, lithium chromate, lithium nitrate, lithium phosphate, lithium borate, lithium perchlorate, lithium tungstate, lithium vanadate, lithium thiocyanate, lithium fluoride, lithium nitrite, In addition to diphenylguanidine, mercaptobenzothiazole, benzotriazole, mixtures of benzotriazole and molybdates, alkanolamines or nitrates, mixtures of lithium hydroxide and lithium molybdate, lithium chromate, lithium nitrate, etc. Examples are given.

However, although these conventional additives are effective in preventing general corrosion of lithium bromide aqueous solutions, they have various drawbacks. For example, chromates, molybdates, nitrates, lithium nitrite, etc. cause crevice corrosion and are themselves reduced and are rapidly consumed, making management complicated. However, when a mixture of benzotriazole or its derivative, molybdate, and lithium hydroxide is added, it lacks corrosion resistance at high temperatures. Addition of lithium hydroxide alone also provides insufficient corrosion protection.

A. The present inventors have investigated how to solve these drawbacks, and have developed a composition comprising an aqueous lithium bromide solution containing lithium hydroxide, an alkali metal salt of molybdic acid, and an alkali metal salt of nitric acid or an alkali metal salt of nitrous acid. In addition, the alkali metal salt of molybdic acid is 0.001 to 0.05% by weight and the alkali metal salt of nitric acid is 0.001 to 0.05% by weight based on the lithium bromide aqueous solution containing lithium hydroxide. 01 to 01 weight percent, and found that the case where the alkali metal salt of nitrous acid is 0.001 to 0.05 weight percent is particularly excellent, and completed the present invention.

The present invention will be explained in more detail below.

The lithium bromide aqueous solution containing lithium hydroxide constituting the composition according to the present invention is obtained by adding lithium hydroxide to a commonly used 53 to 55% by weight aqueous lithium bromide solution.
The lithium hydroxide concentration is adjusted to 0.01-0.03% by weight.

In addition, since the alkali metal salt of molybdic acid, which is another component, is soluble in an aqueous solution of lithium bromide containing lithium hydroxide at least at room temperature or around 40°C, it is easy to handle when distributing the absorption liquid as a product. It's convenient.

The concentration of the alkali metal salt of molybdic acid is not particularly limited, but if it is too small for the lithium bromide aqueous solution containing lithium hydroxide, no effect can be expected, so it is preferably at least 0001%. On the other hand, if it is too much, it tends to promote crevice corrosion, so it is preferable not to exceed 005 heavy duty.

Furthermore, among the alkali metal salts of nitric acid and alkali metal salts of nitrous acid as other constituents, sodium salts and potassium salts are particularly excellent in their ease of use. Regarding the concentration, the effect is weak if the concentration is less than 001% by weight for nitrates and 0001% by weight or less for nitrites, and 01% by weight or less for nitrites.
If it exceeds 1% by weight, or 0.05% by weight in the case of nitrite, both tend to promote crevice corrosion.

The preferred ranges of each component are as described above, but the ranges that are particularly effective in terms of the corrosion inhibiting effect are 0.005 to 005% by weight for alkali metal salts of molybdic acid, 0.005 to 005% by weight for alkali metal salts of nitric acid, is 0
．． 01-0.06% by weight, alkali metal salt of nitrous acid is 0
002-002002-002 It has been known that the effect of containing lithium hydroxide in weight percent is superior to that of lithium bromide alone, but in the present invention, as mentioned above, Lithium 53-55 heavy duty, lithium hydroxide 001
An aqueous solution consisting of ~03 fA% is used.

Next, examples using the composition according to the present invention will be described.

Examples 1 to jO1 Comparative Examples 1 to 4 The effects of the implementation were determined by measuring the corrosion weight loss and the presence or absence of crevice corrosion.

These specific measurement methods will be explained.

To measure the corrosion weight loss, place an aqueous solution containing 0.1% by weight and 1% of lithium hydroxide and 55% by weight and fa of lithium bromide in a molybdenum heating flask (vertically).5. o crnx (horizontal)
3゜Ocm×(thickness) 0.2C! n 232g S
S 41 iJ, a flat plate with a hanging hole was thoroughly polished with emery paper, and the two degreased plates were hung separately and boiled for 1000 hours, and the weight loss was evaluated.

In addition, the presence or absence of crevice corrosion can be determined by placing an aqueous solution of the same silk composition as that used in the corrosion weight loss measurement in the same flask.
(Vertical) 30cm x (Horizontal) 20cTn x (Thickness) 0
．． A silicone rubber band (medium 0
After immersing and boiling for 1,000 hours, a test was made based on the presence or absence of surface corrosion in the area covered with the rubber band.

Table 1 shows the aqueous solution composition and the measured effects of the present invention.

Table 1 (Volume 1) In the example, L was added to a 55% by weight LiBr aqueous solution.
The amount added to an aqueous solution to which 0.1% by weight of iOH was added, and the amount added to a 55% by weight LiBr aqueous solution in the comparative example.

As is clear from the above results, the composition of the present invention is highly effective in preventing corrosion of lithium bromide aqueous solutions.

Patent applicant: Showa Denko Co., Ltd. Agent: Patent attorney Sei Kikuchi

Claims (4)

[Claims] (1) Corrosion-resistant lithium bromide composition consisting of an aqueous lithium bromide solution containing lithium hydroxide, an alkali metal salt of molybdic acid, an alkali metal salt of nitric acid, or an alkali metal salt of nitrous acid. (2) The corrosion-resistant lithium bromide composition according to claim 1, wherein the alkali metal salt of molybdic acid is 0001 to 005% by weight based on the lithium bromide aqueous solution containing lithium hydroxide. (3) The corrosion-resistant lithium bromide composition according to claim 1 or 2, wherein the alkali metal salt of nitric acid is 0.01 to 0.1% by weight based on the lithium bromide aqueous solution containing lithium hydroxide. (4) The alkali metal salt of nitrous acid is 0.001 to 0.05% by weight based on the lithium bromide aqueous solution containing lithium hydroxide.
The corrosion-resistant lithium bromide composition according to claim 1 or 2.