DE1621619A1 - Solution for cleaning aluminum surfaces - Google Patents

Description

METALLGESELLSCHAFT Frankfurt (Main), Nov. 25, 1966

AKTIENGESELLSCHAFT DrBr / BWi
Frankfurt (Main) _

prov. No. 4913 IDZ ID 19

Solution for cleaning aluminum surfaces

It is known to use objects made of aluminum or alloys, which mainly consist of aluminum, to be cleaned or pickled with the help of acidic solutions based on phosphoric acid, After prolonged use of the solutions, however, "severe discoloration of the surfaces often occurred, and it was found that that this was due to an increasing content of the solution in copper, which apparently with the throughput of copper-containing aluminum alloys got into the bath.

It has now been found that such undesired discoloration can be avoided by adding benzotriazole to the solution. In this way, surfaces of aluminum alloys that ^{contain up to about 50} / ° copper can be cleaned with a solution based on phosphoric acid without any disadvantageous consequences.

To achieve a sufficient reduction in discoloration only a small amount of benzotriazole is required, for example 0.05-1% by weight, based on the phosphoric acid,

The phosphoric acid content of the solution is expedient

2 - 20 wt. Ft, preferably 6 - 12 wt. _ ..-

109818/1974

It is beneficial to also use a small amount of the solution add surfactant. The surfactant should preferably not cause foaming, in particular if the solution is used by syringe. Suitable low foam surfactants are good known. Excellent results were z. B. achieved with the product available commercially as "Supronic" B 50, Other useful surfactants are, for example, condensation products of ethylphenol with 9-10 Moles of ethylene oxide and C 16-18 fatty alcohols with 80 Molecules of ethylene oxide are condensed.

The cleaning solutions are generally prepared from concentrates, containing, for example, 50 to 70 Gew.5 $ phosphoric acid (H ₅ PO _4), 0.5 to 2 wt. $ Surfactant, 0.005 to 0.05 Qev.fo benzotriazole and the remainder water . Such concentrates can be diluted by 2 to 30 times their volume with water to prepare the treatment solutions. The treatment solutions need to be replenished after prolonged use. A solution of the same or similar composition as the original treatment solution can be used for this purpose. The cleaning solutions are preferably used by spraying. However, any other application method can also be used. The solutions are preferably used in hot conditions, for example at 40 ~ 65 ⁰ C, with temperatures of 50 -

109818/1974

[35 ^° C. "are preferred. The contact times are generally only a few minutes, for example 2 minutes when spraying.

The cleaning solutions according to the invention are, for example, particularly useful for cleaning beer kegs by spraying, Since it is not necessary to use the solutions when using aluminum drums and stainless steel fittings switch. Both materials are "cleaned" by the acidic solution.

example

A concentrate was prepared which contained 610 parts by weight of phosphoric acid (H ₅ PO ₄ ), 10 parts by weight of "Supronic" B 50 and 1 part by weight of benzotriazole ("Trigard L" from Geigy Ltd.). One part by weight concentrate was diluted with the 5-fold volume of water, so that a cleaning solution, which 20 vol. Containing f "concentrate. Sheets of aluminum alloy containing 0.1 $ copper, were with this solution at 50 - 55 ⁰ G splashed 2 minutes. The panels, which had a soiled appearance before treatment, were bright and clean after treatment and showed no discoloration. Further panels were treated in the solution, this being supplemented with 4.7 liters per 378 liters per point . To supplement the original content of the solution, an addition of 200 ml per liter of solution was required. To this

*) (Polyoxyalkylated polyalkylene glycol, cloud point »at a concentration of 1 #)

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2
At the time, 8.6 m aluminum surface per liter of solution had been splashed and no discoloration had yet occurred.

In another experiment using a corresponding The solution was determined by analysis to be 0.4 p.p.m. prior to contact with the aluminum. Contained copper. After spraying 200 metal sheets (10 cm 5 cm) with the solution, the solution contained 0.8 p.p.m. Copper. No discoloration had occurred and the panels treated were all light and pure.

In a further experiment, an otherwise identical solution was used, to which, however, benzotriazole was not added. After 1000 sheets (10 cm χ 5 cm) of the same alloy had been treated, there was severe discoloration. It was found by analysis that the copper content of the Solution 1.6 p.p.m. fraud.

The discoloration occurs when the copper content of the phosphoric acid Cleaning solutions above about 1 p.p.m. has reached. The copper content can be reduced by adding benzotriazole keep the solutions below values of this order of magnitude.

- Claims - - 5 ■ -

109818/197 //

Claims (2)

Patent claims 1. Solution for cleaning aluminum and aluminum alloys based on phosphoric acid, marked by a content of benzotriazole. 2. Solution according to claim 1, characterized in that it is 0.05-1.0 wt. $, preferably 0.1-0.3 wt. $ Benzotriazole, based on the phosphoric acid, contains. 3 # solution according to claim 1 and 2, characterized in that that they contain 2-20% by weight, preferably 6-12% by weight, of phosphoric acid contains. 4 «solution according to claim 1 - 3» characterized in that that it contains wetting agents. 1098IB / 1