Bismuth compositions for metal pretreatment applications
Provided are bismuth conversion coating compositions that deposit bismuth conversion coatings on a variety of metal substrates, methods of making bismuth conversion coating compositions, methods of depositing bismuth conversion coatings on metal substrates and articles of manufacture having metal surfaces comprising a bismuth conversion coating.
1 . An acidic aqueous bismuth conversion coating composition comprising:
A) dissolved and/or dispersed bismuth;
B) at least one water-soluble aliphatic organic chelating agent present in an amount sufficient to solubilize or disperse A);
C) dissolved copper ions; and
having a pH in a range of from about 2.0 to about 6.
2 . The acidic aqueous bismuth conversion coating composition of claim 1 , wherein A) comprises at least one of dissolved Bi(III) and dissolved and/or dispersed bismuth compounds; B) comprises one or more water soluble aliphatic organic acids and salts thereof selected from linear, branched or cyclic; saturated or unsaturated, C3-C12 hydroxyl-functionalized carboxylic acids and salts thereof.
3 . The acidic aqueous bismuth conversion composition of claim 2 , wherein the one or more water soluble aliphatic organic acids and salts thereof comprise at least one organic polycarboxylic acid and salts thereof.
4 . The acidic aqueous bismuth conversion coating composition of claim 3 , wherein the at least one organic polycarboxylic acid and salts thereof comprises substituted and/or unsubstituted alpha-omega-dicarboxylic acids.
5 . The acidic aqueous bismuth conversion coating composition of claim 4 , wherein the substituted and/or unsubstituted alpha-omega-dicarboxylic acids and salts thereof comprise one or more of substituted and/or unsubstituted propanedioic acid, butanedioic acid, pentanedioic acid, hexanedioic acid, heptanedioic acid, octanedioic acid, nonanedioic acid, decanedioic acid and salts thereof.
6 . The acidic aqueous bismuth conversion coating composition of claim 2 , wherein the one or more water soluble organic carboxylic acids and salts thereof comprises tartaric acid and salts thereof.
7 . The acidic aqueous bismuth conversion coating composition of claim 1 , comprising less than 1 wt. % phosphorus-containing acids and or salts thereof and less than 1 wt. % nickel.
8 . The acidic aqueous bismuth conversion coating composition of claim 1 , comprising one or more additional components selected from the group consisting of a source of free fluoride, nitrate and Si-based substances wherein the Si-based substances are selected from silanes, colloidal SiO 2 and silicates.
9 . The acidic aqueous bismuth conversion coating composition of claim 1 , wherein the acidic aqueous bismuth conversion coating composition comprises at least one pH adjuster and has a pH of about 2.5 to about 5.0.
10 . The acidic aqueous bismuth conversion coating composition of claim 1 , wherein the dissolved and/or dispersed bismuth is present in a total concentration of from about 5 to 10,000 ppm.
11 . The acidic aqueous bismuth conversion coating composition of claim 1 , wherein the dissolved and/or dispersed bismuth comprises one or more of nitrates, oxides and hydroxides of bismuth.
12 . The acidic aqueous bismuth conversion coating composition of claim 1 , wherein the dissolved and/or dispersed bismuth is selected from bismuth nitrate; bismuth nitrate pentahydrate; bismuth subnitrate; bismuth oxide; bismuth hydroxide and combinations thereof.
13 . The acidic aqueous bismuth conversion coating composition of claim 1 , wherein the at least one water-soluble organic chelating agent is present in a total concentration of from about 50 to 100,000 ppm.
14 . A method of depositing a bismuth conversion coating on a substrate having a metal surface, comprising steps of:
a. contacting a metal surface of a substrate, selected from ferrous metal, zinciferous metal and aluminiferous metal, with the acidic aqueous bismuth conversion coating composition of claim 1 for a time sufficient to form a bismuth conversion coating layer on at least a portion of the metal surface; and
b. rinsing the bismuth conversion coating layer with a rinse comprising water.
15 . The method of depositing a bismuth conversion coating of claim 14 further comprising a step c) of subjecting at least a portion of the metal surfaces having the bismuth conversion coating layer to a post-treatment and/or sealing rinse prior to painting.
16 . The method of claim 15 wherein, a step of painting at least a portion of the metal surfaces having the bismuth conversion coating layer with cathodically depositable electrophoretic-dipcoating and wherein after rinsing step b) and before being coated with the cathodically depositable electrophoretic-dipcoating, the metal surfaces are not dried.
17 . A substrate having a metal surface comprising a bismuth conversion coating layer deposited thereon from the acidic aqueous bismuth conversion coating composition of claim 1 , wherein the bismuth conversion coating layer comprises bismuth oxide and/or bismuth hydroxide, and further comprises at least one of elemental Cu, Cu(I) and Cu (II).
18 . An acidic aqueous bismuth conversion coating composition comprising:
A) 100 to 1000 ppm dissolved and/or dispersed bismuth;
B) a complex fluoroacid, or salt thereof and/or one or more water soluble aliphatic organic acids and salts thereof selected from linear, branched or cyclic; saturated or unsaturated C3-C12 organic acids and salts thereof, present in an amount sufficient to solubilize or disperse A);
C) optionally dissolved copper ions; and
at least one pH adjuster, in the form of an acid, base or a buffering acid/base combination present in a quantity sufficient to provide the composition with a pH in a range of from about 2.0-6.0; said composition being capable of producing a conversion coating on CRS that shows no red rusting upon 4 hour immersion in 0.1M NaOH.
19 . The acidic aqueous bismuth conversion coating composition of claim 18 , wherein the complex fluoroacid comprises fluorosilicic acid present in an amount of 1000 ppm to 100,000 ppm; and/or
the aliphatic linear, branched or cyclic; saturated or unsaturated C3-C12 organic acids and salts thereof are hydroxyl-functionalized and present in an amount of 440 ppm to 5400 ppm.