JPS6321754B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a cleaning agent for aluminum metal surfaces containing an alkali and a silicate. Conventionally, an alkaline solution such as caustic soda or soda carbonate has been used to remove organic substances such as oils and fats, proteins, slime, etc., and inorganic substances such as clay, sand, etc. adhering to the aluminum metal surface. Since these alkaline solutions have little cleaning effect unless they are in the strongly alkaline range, a cleaning solution with a pH of 11 or higher is usually required. Therefore, the alkali concentration must be high, and usually a high concentration of 1% or more is required. This highly concentrated alkaline solution was not only extremely dangerous to handle, but also had the disadvantage of severely corroding metal surfaces. For this reason, polymeric substances such as gum arabic and gum tragacanth, sodium silicate, and the like have been used to suppress corrosion of aluminum metal surfaces in alkaline solutions. However, polymeric materials are not only expensive but also do not have sufficient corrosion inhibiting effects. On the other hand, sodium silicate is said to be inexpensive and has an anti-corrosion effect.
(1975), sodium silicate was added as SiO ₂ to 0.94 mol/Na ₂ CO ₃ aqueous solution and 0.0025 mol to 0.01 mol/
(In the case of Sodium Silicate No. 3) It is described that it is added to prevent corrosion of aluminum metal. Here, the molar ratio of sodium silicate to alkali as SiO ₂ is 0.0027 to 0.01. However, even with this method, it was difficult to obtain a good corrosion inhibiting effect. An object of the present invention is to provide a cleaning agent that has excellent cleaning effects without causing corrosion of the aluminum metal surface. The present inventors have conducted intensive research on cleaning technology and anti-corrosion technology for aluminum metal, and have discovered that the concentration of sodium silicate required to suppress metal corrosion differs depending on the concentration of alkali, and that sodium silicate suppresses metal corrosion. We have discovered that this works effectively not only in terms of cleaning power, but also in terms of detergency, leading to the present invention. That is, the present invention provides an aluminum metal surface cleaning agent containing an alkali consisting of sodium hydroxide and a silicate, in which the alkali is added in an amount of 0.001 to 4.0 mol/
Contains alkali of 0.001 mol/more than 2.0 mol/
If the amount is less than 0.25 mol/mol or more and 2.5 mol/mol of the silicate as SiO ₂ relative to the alkali,
Contains alkali at the following concentration: 2.0 to 4.0 mol/
The case is characterized by containing silicate at a concentration of 0.5 to 2.5 mol/SiO ₂ . The concentration of alkali consisting of sodium hydroxide is
It is necessary that the amount is 0.001 to 4.0 mol/.
If it is lower than 0.001 mol/, the cleaning effect will be poor,
If it is higher than 4.0 mol/mol, the viscosity becomes high and it becomes difficult to handle. Regarding the concentration of silicate, if it is lower than the lower limit, the anticorrosive effect will be poor, and if it is higher than the upper limit, insoluble salts of silicic acid, such as calcium silicate, will be produced, so it is not preferable that it exceeds 2.5 mol/mol. Silicates include sodium silicate and potassium silicate, and sodium silicate includes sodium silicate No. 1, No. 2, and No. 3 according to JIS standards. Sodium silicate No. 3 is mass-produced and therefore inexpensive, and has a high SiO ₂ content, making it highly effective and preferred. The cleaning agent of the present invention has a pH of 10 to 14. Also,
To clean an aluminum metal surface using the cleaning agent of the present invention, the metal surface may be sprayed with the cleaning agent or immersed in a cleaning agent solution to dissolve and remove deposits, and then washed with water. In addition, in the present invention, nonionic surfactants and
Synthetic detergents such as ABS can be used together. Further, known anticorrosive agents such as gum arabic, gum tragacanth, and sodium alginate can also be used in combination. In this case, the concentration of silicate can be reduced somewhat. According to the present invention, by maintaining the concentration of silicate in accordance with the concentration of alkali consisting of sodium hydroxide, there is no fear of corrosion of the metal surface.
The cleaning effect can also be dramatically improved compared to a solution containing only alkali or a known solution containing sodium silicate. Example 1 Test piece (Al, JIS-A-1050, Hard H-
22, plate thickness 0.12 mm, effective area 30 cm ² ), corrosion tests and cleaning tests were conducted. <Corrosion test> Test liquid (alkali consisting of sodium hydroxide +
Put 200c.c. of silicate into a beaker, immerse a weighed test piece in it, and heat it at 20℃ for 30 minutes.
It was left standing for a minute. The test piece was then pulled out, washed with water, and air-dried. The surface condition of this product was observed to determine the corrosion status, and the weight was measured to determine the corrosion loss. <Cleaning test> Tobacco water husks were collected in 10 buckets and soaked in ethyl alcohol, and the extract was extracted overnight. After filtering the extract, it was concentrated to 100 c.c. using a rotary evaporator. The test piece was immersed in the concentrated liquid, pulled out, and air-dried. Immerse the contaminated test piece in the test solution for 30 minutes at 20°C.
The cleaning effect was investigated by observing the state of dirt adhesion after lifting. The above test results are shown in Table 1 along with the compounds and concentrations used in the test solution. The composition of silicate soda No. 3 is 30% SiO ₂ , 10% Na ₂ O, and 60% H _{2 O.}

【table】

[Table] Indicates that there is no. In the cleaning effect column, × means no effect, △ means somewhat effective, ○ means good, and ◎
indicates very good condition.
Example 2 A test similar to Example 1 was conducted using a test solution to which NaOH and silicate were added, as well as gum arabic and a nonionic surfactant (polyoxyethylene nonylphenol ether). The results are shown in Table 2.

【table】

[Table] Example 3 A cleaning solution containing 0.2 w/v% (0.05 mol/) of NaOH and 1 w/v% (0.05 mol/) of sodium silicate No. I did some cleaning. The aluminum fin had turned black due to cigarette tar, cooking oil, and dust, reducing its cooling efficiency. After covering the aluminum fin with vinyl to prevent the cleaning solution from getting on other parts,
A cleaning solution of about 5% was sprayed using a sprayer and immediately washed with water. As a result, the aluminum fin became clean and cooling efficiency was restored. Further, no corrosion was observed on the aluminum fin.

Claims (1)

[Claims] 1. In an aluminum metal surface cleaning agent containing an alkali consisting of sodium hydroxide and a silicate, if the alkali is contained in an amount of 0.001 to 4.0 mol/ or more and less than 2.0 mol/, the silicate is replaced with SiO ₂ , it must be contained in a concentration of 0.25 mol/mol or more and 2.5 mol/mol or less relative to alkali, and if the alkali is 2.0 to 4.0 mol/mol, it must contain silicate in a concentration of 0.5 to 2.5 mol/mol as SiO ₂ . A cleaning agent for aluminum metal surfaces.