Optimized process control in the anti-corrosive metal pretreatment based on fluoride-containing baths

Patent metadata

Field	Value
Publication number	US-10458022-B2
Application number	US-201715618229-A
Country	US
Kind code	B2
Filing date	Jun 9, 2017
Priority date	Dec 12, 2014
Publication date	Oct 29, 2019
Grant date	Oct 29, 2019

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.

First claim

What is claimed is:

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/m 2 to 0.7 mmol/m 2 , 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:

VW
=

z
E

-
2.4

2.8
⁢

⁢
mmol
⁢

⁢

L

-
1

-

c
B
Me

⁡

(

z
E

-
6

)

·

10

-
1

⁢

⁢
mmol
⁢

⁢

m

-
2

(
I
)

where
VW: discarded amount of pretreatment solution in L/m 2 ;
C B Me : concentration of zirconium and/or titanium in the pretreatment solution in mmol/L;
Z E : 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 replenishment solutions, with the proviso that the following applies:

z
E

<

2.8
⁢

⁢
mmol
⁢

⁢

L

-
1

c
B
Me

+
6.

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

z
E

<

0.4
⁢

⁢
mmol
⁢

⁢

L

-
1

c
B
Me

+
6.

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:

VW
=

7
⁢

(

Assignees

• Henkel Ag & Co Kgaa

Inventors

• Brouwer Jan-Willem
• Stromberg Christian
• Pilarek Frank-Oliver
• Kroemer Jens
• Resano Artalejo Fernando Jose
• Henze Natascha

Classifications

• C23C22/86

  Regeneration of coating baths · CPC title

• C23C22/34 Primary

  containing fluorides or complex fluorides · CPC title