OPTIMIZED PROCESS CONTROL IN THE ANTI-CORROSIVE METAL PRETREATMENT BASED ON FLUORIDE-CONTAINING BATHS

• US 20170283955A1
• Filed: 06/09/2017
• Published: 10/05/2017
• Est. Priority Date: 12/12/2014
• Status: Active Grant

• Current Assignee: Henkel AG & Co KGaA
• Original Assignee: Henkel AG & Co KGaA
• Inventors: Brouwer, Jan-Willem, Stromberg, Christian, Pilarek, Frank-Oliver, Kroemer, Jens, Resano Artalejo, Fernando Jose, Henze, Natascha
• Granted Patent: US 10,458,022 B2
• Time in Patent Office: Days
• CPC Class Codes: C23C 22/34 containing fluorides or complex fluorides
• CPC Class Codes: C23C 22/86 Regeneration of coating baths

Abstract

A method for corrosion protection treatment, comprising contacting a series of components having metallic surfaces of iron and/or zinc with a passivating aqueous pretreatment solution, present in a system tank, containing compounds of the elements zirconium and/or titanium, and contacting with a source of fluoride ions wherein a portion of the pretreatment solution is discarded and replaced with a volume portion of one or more such replenishment solutions which in total are at least of equal size, by metered addition to the system tank of the pretreatment and wherein discarding as a function of the molar ratio of the elements fluorine to zirconium and/or titanium must not drop below a predefined value, the metered addition of replenishment solution takes place such that maintaining the concentration of the elements zirconium and/or titanium in the passivating aqueous pretreatment solution in the form of water-soluble compounds is ensured.

Claims

1. A method for anti-corrosive treatment of metallic surfaces, in a serial operation, comprising steps of:

a, contacting in a serial operation a plurality of metallic surfaces of components comprising zinc and/or iron with a passivating aqueous pretreatment solution located in a system tank at a temperature of less than 50°

C., the passivating aqueous pretreatment solution comprising one or more water-soluble compounds of the elements zirconium and/or titanium and one or more water-soluble compounds that represent a source for fluoride ions, for a time such that a layer coating of 0.1 mmol/m² to 0.7 mmol/m², based on the elements zirconium and/or titanium, results on the metallic surfaces of zinc and/or iron; and

,

b. during the anti-corrosive treatment, discarding a portion of the passivating aqueous pretreatment solution of the system tank and replacing said portion with, in sum, at least equal parts by volume of one or more replenishment solutions by addition into the system tank such that concentration of the elements zirconium and/or titanium in total in the passivating aqueous pretreatment solution in the form of water-soluble compounds is maintained at 0.05 mmol/L to less than 0.8 mmol/L, and a molar ratio of a total amount of fluorine in the form of water-soluble compounds that represent a source for fluoride ions to a total amount of the elements zirconium and/or titanium in the form of water-soluble compounds in an added total volume of replenishment solutions is less than the same molar ratio in the passivating aqueous pretreatment solution, but no less than 4.5, and a discarded amount of passivating aqueous pretreatment solution in liters per serially treated square meter of metallic surfaces of zinc and iron exhibits at least a value according to Formula I;

2. The method according to claim 1, wherein the molar ratio Z_E meets:

3. The method according to claim 2, wherein the discarded amount of passivating aqueous treatment solution is no greater than a value according to Formula II, in liters per serially treated square meter of metallic component:

4. The method according to claim 1, wherein the molar ratio of the total amount of fluorine in the form of water-soluble compounds that represent a source for fluoride ions to the total amount of the elements zirconium and/or titanium in the form of water-soluble compounds in the added total volume of the replenishment solutions is no less than 5.0.

5. The method according to claim 1, wherein the molar ratio of the total amount of the elements zirconium and/or titanium in the form of water-soluble compounds to a respective total amount of one of the elements calcium, magnesium, aluminum, boron, iron, manganese or tungsten in the form of water-soluble compounds in the added total volume of the replenishment solutions is greater than 5:

1. 6, The method according to claim 1, wherein the passivating aqueous pretreatment solution in the system tank in total comprises less than 0.55 mmol/L water-soluble compounds of the elements zirconium and/or titanium.

7. The method according to claim 1, wherein the passivating aqueous pretreatment solution has a pH value of no less than 3.0, and no greater than 5.0.

8. The method according to claim 1, wherein the passivating aqueous pretreatment solution has a temperature of no greater than 40°

C.

9. The method according to claim 1, wherein the discarding of passivating aqueous pretreatment solution takes place by dragging out pretreatment solution with every component of the series of components to be treated, and by actively discharging pretreatment solution, each out of the system tank of the pretreatment.

10. The method according to claim 9, wherein the discarding by way of active discharging of passivating aqueous pretreatment solution takes place discontinuously after a defined number n of components i has been pretreated, the discontinuous discarding assuming at least a value according to Formula Ill in liters for a serially treated number n of components i:

11. The method according to claim 10, wherein the discontinuously discarded amount in liters for a serially treated number n of components i does not exceed a value according to Formula IV

12. The method according to claim 9, wherein the discarding takes place by actively discharging passivating aqueous pretreatment solution and continuously replacing discarded pretreatment solution with one or more replenishment solutions during the pretreatment of the components in a serial operation by feeding a constant volume flow of replacing replenishment solution into the system tank of the pretreatment, the continuous discarding of passivating aqueous pretreatment solution being implemented predominantly by way of spillover of the system tank.

13. The method according to claim 12, wherein the continuously discarded amount assumes at least a value according to Formula V, in liters per serially treated square meter of metallic surfaces of zinc and iron:

14. The method according to claim 13, wherein the continuously discarded amount in liters per serially treated square meter of metallic surfaces of zinc and iron does not exceed a value according to Formula VI:

15. The method according to claim 1, further comprising a dip coating step carried out after the contacting step a.), with or without interposed rinsing steps.

16. The method according to claim 15, wherein, after the contacting step a.), no further treatment step follows using an aqueous solution comprising more than 10% of the concentration of the passivating aqueous pretreatment solution of water-soluble compounds of the elements zirconium and/or titanium.

17. The method according to claim 16, wherein, after the contacting step a.), no further treatment step follows which is used to form a coating comprising substrate-foreign metallic or metalloid elements having a layer coating of more than 0.1 mmol/m² based on said substrate-foreign elements, on at least one metal surface of the component.

18. The method according to claim 15, further comprising a rinsing step carried out immediately after the contacting step a.), the rinsing step comprising bringing the components in contact with a rinsing solution located in a rinsing solution system tank, wherein, during the anti-corrosive treatment of the components in a serial operation, a portion of the rinsing solution is discarded and replaced with at least equal parts by volume of a replenishing rinsing solution, which in total comprises less than 10⁻

5 mol/L water-soluble compounds of the elements zirconium and/or titanium, and less than 10<sup>−

4</sup> mol/L water-soluble compounds that represent a source for fluoride ions, based on the element fluorine.