Etching agent for aluminum or aluminum alloy

Abstract

A composition of an etching agent for aluminum or aluminum alloy and a treatment method thereof are provided. The etching agent does not contain a component not suitable for a wastewater treatment, such as boron and fluorine, and has stable etching performance even when performing an etching treatment continuously. The etching agent has excellent aging resistance providing good etching uniformity and corrosion resistance after etching. This etching agent is an etching agent for aluminum or aluminum alloy, including 50 parts by mass of an aminocarboxylic acid, 5 to 300 parts by mass of at least one selected from a hydroxycarboxylic acid, a dicarboxylic acid, a polycarboxylic acid, and salts thereof, and 10 to 800 parts by mass of at least one selected from a hydroxide, a carbonate, and a bicarbonate of an alkali metal, wherein an aqueous solution of the etching agent has a pH of 8 to 10.

Description

TECHNICAL FIELD[0001]The present invention relates to a metal surface treatment technique. More specifically, the present invention relates to an etching technique for aluminum or aluminum alloy.BACKGROUND ART[0002]Conversion to environmentally friendly technology is required in the aluminum surface treatment industry responding to the increased recent interest in environmental problems. Etching for aluminum or aluminum alloy is used for, for example, cleaning of the surface of a processed and molded aluminum as well as for pretreatment for coating or bonding, plating, and welding.[0003]A surface of aluminum or aluminum alloy is covered with a stable oxidized film in neutrality. For performing etching, the oxidized film first needs to be dissolved. For this reason, an acidic agent containing hydrofluoric acid or a strong alkaline agent including sodium hydroxide has been generally used as an etching agent for the oxidized film.[0004]By using the acidic etching agent, including a hyd...

AI Technical Summary

Benefits of technology

The present invention provides an etching agent for aluminum or aluminum alloy that can remove smut and dirt while maintaining the original corrosion resistance of aluminum. The etching agent can be used as a pretreatment for bonding or coating with an active substance paste, and can provide a surface with excellent bondability and adhesion. Therefore, the etching agent can be widely used in the surface treatment of aluminum components or members, such as batteries or capacitors.

Problems solved by technology

However, with respect to the acidic etching agent, handling is dangerous, and a wastewater treatment is difficult to perform.

Therefore, there has been a problem in terms of environment and safety.

However, this type of etching agent has had problems in that etching is not uniform, variations of an etching rate to an etching treatment temperature or time are large, and a safe treatment is difficult to perform.

For this reason, use of the etching agent including boron is also regulated, and costs for wastewater treatment increase.

However, a treatment liquid having the above composition relatively shortens a time for removing an oxidized film, but hardly controls the reaction.

For example, there has been a problem in that decrease of a treatment temperature significantly reduces etching performance.

Also, there has been a problem in that accumulated aluminum ions reduce etching performance when the treatment is continued.

In this technique, etching performance is unlikely to decline even when a treatment is continued.

However, when an etching treatment is continued for a relatively long time, dissolved aluminum ions increase in concentration.

Thus, there has been remained a problem that addition of aluminum or calcium as an ion is not enough to inhibit the decline of etching performance.

To compensate for the problems, an etching treatment liquid needs to be frequently renewed and thus excessive waste water is generated.

For this reason, an environmental problem has been still remained.