JPS589157B2 - Kinzokuno Fushiyokuboushisoseibutsu - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composition for inhibiting corrosion of metals in contact with water, such as circulating cooling water.

Conventionally, chromium compounds such as sodium dichromate and phosphates such as sodium hexametaphosphate are known to be effective alone as corrosion inhibitors for industrial water such as circulating cooling water. In addition, zinc salts such as zinc sulfate and zinc chloride or nitrites such as sodium nitrite and ammonium nitrite are used in combination with oxycarboxylic acids, which have little anticorrosion effect when used alone or with their salts. It is also known to exhibit excellent anticorrosion effects.

These anticorrosive agents have been widely used in this type of industry due to their excellent anticorrosion effects, but they are not effective unless they are used in relatively large amounts, usually on the order of 100 ppm relative to the water being treated. Industrial water added with these anticorrosive agents causes significant water pollution due to its wastewater.
Currently, the problem of wastewater pollution is becoming particularly serious, and the use of both chromium compounds and lead salts is now strictly regulated.

Furthermore, it has recently become clear that phosphates serve as a nutritional source for microorganisms, and their use is gradually being regulated.

Furthermore, nitrites are toxic to humans and fish, and have the disadvantage of causing environmental pollution.

Therefore, the industry has been forced to stop using the above-mentioned compounds that have been widely used in the past, and there is a demand for research and development of new anticorrosive agents to replace these anticorrosive agents.

The present inventors have conducted various studies in order to meet the above demands.

As a result, it has never been used as an anticorrosive agent,
Moreover, when at least one of ammonium molybdate, sodium perborate, and sodium percarbonate, which do not have anticorrosive properties when used alone, is used in combination with oxycarboxylic acid and/or its salts in a predetermined ratio, these compounds themselves are considered to be harmful to pollution. In addition, it is not subject to any regulations, and even when used at a concentration of about 1/5 of that of conventional corrosion inhibitors, the synergistic effect of the two types of compounds mentioned above makes it comparable to or even better than conventional corrosion inhibitors. The present inventors have discovered that it is possible to exhibit the above-mentioned anticorrosion effect, and have now completed the present invention.

That is, the present invention provides oxycarboxylic acids and/or salts thereof (hereinafter simply referred to as oxycarboxylic acids) 80-9
0% by weight and at least one of ammonium molybdate, sodium perborate and soda percarbonate 10 to 20% by weight
A pollution-free corrosion inhibiting composition for metals in contact with water, characterized by containing as an active ingredient.

The corrosion-inhibiting composition of the present invention not only does not contain any harmful substances that pose a pollution problem, but also exhibits a sufficient effect even when used in a relatively small amount, so that there is no water pollution caused by its wastewater.

Furthermore, there is no decrease in the anticorrosion effect due to adhesion of scales such as calcium phosphate caused by phosphate groups to metals, which is seen in conventional anticorrosive agents that use phosphates, and the product exhibits an extremely excellent anticorrosion effect. .

The oxycarboxylic acids used in the present invention include:
For example, various oxycarboxylic acids such as tartaric acid, citric acid, gluconic acid, etc. can be used.

Water-soluble salts of these salts, such as sodium salts, potassium salts, and ammonium salts, can also be used in the same manner.

However, the present invention requires the use of at least one of ammonium molybdate, sodium perborate, and soda percarbonate in addition to the above-mentioned oxycarboxylic acids.

None of these compounds poses the risk of causing water pollution, and moreover, exhibits an extremely excellent anticorrosion effect due to their synergistic action with the above-mentioned oxycarboxylic acids.

Each of these compounds usually has a 10 to 10
By adding 20% by weight, a suitable anticorrosion effect can be exhibited.

Further, in the corrosion-inhibiting composition of the present invention, each component can be added to the water to be treated, either separately or in the form of a mixture in advance, similar to conventional anti-corrosive agents comprising oxycarboxylic acids and phosphates.

Although the amount used varies depending on the quality of the water to be treated, usually 50 to 100 ppm of this anticorrosive agent is initially added to the water to be treated at the start of operation of the cooling system, and most of it is absorbed into the metals in the system. During continuous operation, the desired effect can be sufficiently exerted by simply adding it in a range of 10 to 30 ppm to the treated water to be replenished.

Therefore, the amount discharged into wastewater will not exceed 30 ppm.

As mentioned above, the corrosion inhibiting composition of the present invention exhibits the same or better effect than conventional corrosion inhibitors when used in a much smaller amount, and there is no risk of causing any pollution problems due to its drainage.

EXAMPLES Below, in order to explain the present invention in more detail, Examples and Comparative Examples will be given and explained.

Example 1 Tartaric acid and sodium perborate (NaB03.4H2O, molecular weight 153.88, same hereinafter) were mixed in a weight ratio of 90:10 to prepare a corrosion-inhibiting composition of the present invention.

Next, this anticorrosive agent was added to industrial water with a pH of 7.0 to 7.5, a calcium hardness of 70 ppm, and an electrical conductivity of 240 μU.
0 ppm was added, heated to 50 ± 1°C in a water bath, a mild steel test piece (SS-41, weight approximately 102) was immersed, and the water was stirred with a magnetic stirrer for 3
When the corrosion rate was measured after being left for one day, a significantly low value of 2.8 mdd was obtained.

There was still almost no scale adhering to this mild steel test piece, and no rust lumps had occurred at all.

Examples 2 to 5 Corrosion-inhibiting compositions of the present invention were prepared using each compound shown in Table 1 below at a predetermined mixing ratio.

A predetermined amount of each corrosion inhibitor was then added to the same industrial water used in Example 1, and a corrosion test was then conducted in the same manner as in Example 1.

The results are shown in Table 2.

For comparison, the results in the case where no corrosion inhibitor was added are also shown.

Comparative Examples 1 to 9 Corrosion tests were conducted in the same manner as in Example 1 using the known anticorrosive agents shown in Table 1 and each component used in the present invention alone.

The results are shown in Table 2.

In Table 1, sodium percarbonate is 2Na2CO
A commercially available product having a molecular weight of 174.0 and 3.3H2O2 was used.

Furthermore, Comparative Example 1* in Table 2 shows the case where the anticorrosive sample listed in Table 1 was used at a concentration of 150 ppm (the conventionally used amount).

From Table 2 above, it is clear that the anticorrosive agent of the present invention, when added in an amount of 30 ppm, can exhibit a greater anticorrosion effect than when the conventional sodium dichromate is added in an amount of 150 ppm.

Furthermore, ammonium molybdate, sodium perborate, sodium percarbonate, and tartaric acid alone can exhibit no corrosion-preventing effect; on the contrary, ammonium molybdate, traditionally known as an oxidizing agent, has been shown to promote corrosion. [Fish toxicity test] Fish toxicity tests, which are considered to be one type of water pollution, were conducted on the corrosion inhibitors of the present invention (Examples 1, 3, and 4) and conventional corrosion inhibitors (Comparative Examples 1 and 3) as follows. did.

That is, according to the "Factory Effluent Test Method" described in JISK-0102, the test fish was the Japanese medaka (average weight 1 g, average body length 2 cm), and the concentration (ppm) at which 50% of the fish died after 48 hours at a water temperature of 17°C was ) was determined as TLm (48hr).

The results obtained are shown in Table 3 below.

As is clear from Table 3 above, the anticorrosive agent of the present invention needs to be concentrated 10 to 60 times in order to have the same level of fish toxicity as the conventional anticorrosive agent. Moreover, it has extremely low toxicity to the extent that it can be said that it is not toxic to fish at all.

Claims (1)

[Claims] 1-oxycarboxylic acid and/or its salts 80-9
0% by weight and 10-20% by weight of at least one of ammonium molybdate, sodium perborate and soda percarbonate.
A pollution-free corrosion-inhibiting composition for metals in contact with water, characterized by containing as an active ingredient.