Phosphate coating composition and method of applying a zinc-nickel phosphate coating

• US 4,793,867 A
• Filed: 09/26/1986
• Issued: 12/27/1988
• Est. Priority Date: 09/26/1986
• Status: Expired due to Fees

• Current Assignee: PPG Industries Incorporated (Nouryon BV)
• Original Assignee: Chemfil Corporation
• Inventors: Cape, Thomas W., Charles, Harry R., Miles, Donald L.
• Primary Examiner(s): Silverberg, Sam
• Application Number:
  US06/912,754
• Time in Patent Office: 823 Days
• Field of Search: 148/6.15 Z
• US Class Current: 148/254
• CPC Class Codes: C23C 22/12 containing zinc cations
• CPC Class Codes: C23C 22/18 containing manganese cations
• CPC Class Codes: C23C 22/182 containing also zinc cations
• CPC Class Codes: C23C 22/184 containing also nickel cations
• CPC Class Codes: C23C 22/362 containing also zinc cations
• CPC Class Codes: C23C 22/364 containing also manganese cations

Abstract

This invention relates to a method of coating metal surfaces including zinc-coated steel with zinc and nickel phosphate crystals for the purposes of improving paint adhesion, corrosion resistance, and resistance to alkali solubility. Potassium, sodium, or ammonium ions present as a phosphate salt are combined with zinc ions and nickel or manganese ions in relative proportions to cause the nickel or manganese ions to form a crystalline coating on the surface in combination with the zinc and phosphate.

Claims

1. A method of phosphate conversion coating metallic substrates selected from the group consisting of steel, zinc-coated steel, and aluminum comprising the steps of:

cleaning the surface of the substrates with an alkali cleaner;

conditioning the surface of the substrates with a titanium containing aqueous solution;

coating the surface of the substrates with a solution consisting essentially of an aqueous solution of the constituents A, B, and C combined in the ratio of 8 to 20 parts by weight A;

2 parts by weight B;

2-4 parts by weight C, and B is provided at a concentration of between about 300 ppm and 750 ppm,

wherein

A is selected from the group consisting of potassium, sodium and ammonium ions present as a phosphate salt;

B is zinc ions; and

,

C is selected from the group consisting of nickel, or nickel and manganese wherein the concentration of C does not exceed 1500 ppm;

applying said coating composition to the surface of the substrates at a temperature of between about 100° and

140°

F. for between 30 and 300 seconds; and

rinsing said substrates.

2. The method of claim 1 wherein said constituents are combined in a ratio of about from 8 to 20 parts by weight A:

2 parts by weight B;

2 to 4 parts by weight C, and the concentration of B is between about 500 to 700 ppm.

3. The method of claim 1 wherein said constituents are combined in a ratio of about 10 parts by weight A:

2 parts by weight B;

3 parts by weight C, and the concentration of B is between about 500 to 700 ppm.

4. A method of coating substrates selected from the group consisting of steel, zinc-coated steel, and aluminum comprising the steps of:

cleaning the substrates with an alkali cleaner;

conditioning the surface of the substrates with an aqueous solution of Jernsted salts;

preparing a coating composition by diluting in an aqueous bath first and second concentrates;

said first concentrate consisting essentially of in weight percent;

space="preserve" listing-type="tabular">______________________________________ Water 0-80% Phosphoric Acid (75%) 10-60% Nitric Acid (67%) 2-35% Zinc Oxide 2-15% Nickel Oxide 1.5-25% Sodium Hydroxide (50%) 0-10% Ammonium Bifluoride 0-10% Sodium Salt of 2 Ethyl 0-1% Hexyl Sulfate Nitro Benzene Sulfonic 0-trace % Acid ______________________________________

said second concentrate consisting essentially of in weight percent;

space="preserve" listing-type="tabular">______________________________________ Water 30-80% Phosphoric Acid (75%) 10-35% Nitric Acid 0-15% Sodium Hydroxide (50%) 0-30% Potassium Hydroxide (45%) 0-45% ______________________________________

said aqueous bath having a zinc ion concentration of between about 300 and 750 ppm, an alkali metal ion concentration from an alkali metal phosphate of between about 1,200 and 10,000 ppm, and a nickel ion concentration of between about 300 and 1,500 ppm;

applying said coating composition to the surface of the substrates at a temperature of between about 100° and

140°

F. for between 30 and 300 seconds;

rinsing said substrates;

applying a chromate rinse to the substrates; and

rinsing said substrates with water.

5. A method of coating a substrate selected from the group consisting of steel, zinc-coated steel, and aluminum comprising the steps of:

cleaning the substrates with an alkali cleaner;

conditioning the surface of the substrates with an aqueous solution of Jernsted salts;

preparing a coating composition by diluting in an aqueous bath first and second concentrates;

said first concentrate consisting essentially of in weight percent;

space="preserve" listing-type="tabular">______________________________________ Water 10-50% Phosphoric Acid (75%) 20-45% Nitric Acid (67%) 5-25% Zinc Oxide 4-9% Nickel Oxide 3-18% Sodium Hydroxide (50%) 0-6% Ammonium Bifluoride 0.2-5% Sodium Salt of 2 Ethyl 0.2-0.5% Hexyl Sulfate Nitro Benzene Sulfonic 0-trace % Acid ______________________________________

said second concentrate consisting essentially of in weight percent;

space="preserve" listing-type="tabular">______________________________________ Water 30-60% Phosphoric Acid (75%) 20-35% Nitric Acid 0-10% Sodium Hydroxide (50%) 0-30% Potassium Hydroxide (45%) 0-45% ______________________________________

said aqueous bath having a zinc ion concentration of between about 500 and 700 ppm, an alkali metal hydroxide ion concentration of between about 2000 and 7000 ppm, and a nickel ion concentration of between about 500 and 1,050 ppm;

applying said coating composition to the surface of the substrates at a temperature of between about 100° and

140°

F. for between 30 and 300 seconds;

rinsing said substrates;

applying a sealing rinse to the substrates; and

rinsing said substrates with water.

6. A method of coating a substrate selected from the group consisting of steel, zinc-coated steel, and aluminum comprising the steps of:

cleaning the substrates with an alkali cleaner;

conditioning the surface of the substrates with an aqueous solution of Jernsted salts;

preparing a coating composition by diluting in an aqueous bath first and second concentrates;

said first concentrate consisting essentially of in weight percent;

space="preserve" listing-type="tabular">______________________________________ Water 20% Phosphoric Acid (75%) 38% Nitric Acid (67%) 21% Zinc Oxide 5% Nickel Oxide 8% Sodium Hydroxide (50%) 4% Ammonium Bifluoride 2% Sodium Salt of 2 Ethyl 0.3% Hexyl Sulfate Nitro Benzene Sulfonic trace % Acid ______________________________________

said second concentrate consisting essentially of in weight percent;

space="preserve" listing-type="tabular">______________________________________ Water 34% Phosphoric Acid (75%) 28% Nitric Acid 5% Sodium Hydroxide (50%) 13% Potassium Hydroxide (45%) 20% ______________________________________

said aqueous bath having a zinc ion concentration of between about 500 and 700 ppm, an alkali metal hydroxide ion concentration of between about 2000 and 7000 ppm, and a nickel ion concentration of between about 3000 and 1,050 ppm;

applying said coating composition to the surface of the substrates at a temperature of between about 100° and

140°

F. for between 30 and 300 seconds;

rinsing said substrates;

applying a chromate rinse to the substrates; and

rinsing said substrates with water.