Method for coating metallic surfaces with a composition that is rich in silane

Abstract

Pre-coating of a metal surface prior to further coating or other treatment uses an aqueous composition wholly or mainly free of chromium (VI) compounds and is such that (a) the composition contains (i) an at least partially hydrolyzable silane and (ii) a metal chelate; and (b) the cleaned, etched or pretreated metal is contacted with the composition and the formed film is dried (and optionally hardened) to a thickness of 0.01-10 mu . Independent claims are also included for (1) the process in which the aqueous composition also contains (iii) an organic film-former comprising a water-soluble or -dispersible (co)polymer of acid number 3-250 and (iv) a long-chain alcohol film-forming aid.; and (2) compositions containing (i) and (ii) at 0.1-10 : 1 ratio and optionally also (iii) and (iv) .

Description

technical field

[0001] The present invention relates to a method of coating a metal surface with an aqueous composition comprising a silane and a metal chelating agent and optionally an organic film former. The invention also relates to the use of corresponding aqueous compositions and substrates coated according to the method of the invention. Background technique

[0002] The method most commonly employed hitherto as a surface treatment or pretreatment on metals, especially metal strips, prior to painting is based on the application of chromium(III) and / or chromium(VI) compounds together with various additives. Due to the toxicological and ecological risks associated with such methods and also due to the foreseeable legal restrictions on the use of chromate-containing methods, alternatives to these methods have long been sought in all areas of metal surface treatment.

[0003] The use of silanes for the preparation of aqueous compositions for silicone-rich corrosion prote...

Examples

example and comparative example

[0240] The examples described below are intended to describe the subject-matter of the invention in more detail.

[0241] A) Compositions mainly based on chelating agents and silanes:

[0242]For the preparation of the aqueous concentrate, at least one partially hydrolyzed silane is aged for at least 2 weeks and optionally hydrolyzed thereby. Subsequently, the metal chelating agent listed in Table 1 was added. Subsequently, this concentrate is diluted with water, optionally with the addition of agents for adjusting the pH, such as ammonia, in order to obtain a ready-to-use treatment solution. In each case, at least 3 pieces of hot-dip galvanized steel or Galvalume  The steel plates were contacted with the corresponding treatment solution at 25°C by roll coating and drying. The metal sheets thus treated were dried at 90°C PMT and subsequently tested for their corrosion protection capabilities.

[0243] Examples E1-E8, including Comparative Example CE4, show the effect of...

technical field

[0001] The present invention relates to a method of coating a metal surface with an aqueous composition comprising a silane and a metal chelating agent and optionally an organic film former. The invention also relates to the use of corresponding aqueous compositions and substrates coated according to the method of the invention. Background technique

[0002] The method most commonly employed hitherto as a surface treatment or pretreatment on metals, especially metal strips, prior to painting is based on the application of chromium(III) and / or chromium(VI) compounds together with various additives. Due to the toxicological and ecological risks associated with such methods and also due to the foreseeable legal restrictions on the use of chromate-containing methods, alternatives to these methods have long been sought in all areas of metal surface treatment.

[0003] The use of silanes for the preparation of aqueous compositions for silicone-rich corrosion prote...

Examples

example and comparative example

[0240] The examples described below are intended to describe the subject-matter of the invention in more detail.

[0241] A) Compositions mainly based on chelating agents and silanes:

[0242]For the preparation of the aqueous concentrate, at least one partially hydrolyzed silane is aged for at least 2 weeks and optionally hydrolyzed thereby. Subsequently, the metal chelating agent listed in Table 1 was added. Subsequently, this concentrate is diluted with water, optionally with the addition of agents for adjusting the pH, such as ammonia, in order to obtain a ready-to-use treatment solution. In each case, at least 3 pieces of hot-dip galvanized steel or Galvalume  The steel plates were contacted with the corresponding treatment solution at 25°C by roll coating and drying. The metal sheets thus treated were dried at 90°C PMT and subsequently tested for their corrosion protection capabilities.

[0243] Examples E1-E8, including Comparative Example CE4, show the effect of...