Method for zinc phosphating metal components in series in a sludge-free manner so as to form layers

Patent metadata

Field	Value
Publication number	US-2020032402-A1
Application number	US-201916593520-A
Country	US
Kind code	A1
Filing date	Oct 4, 2019
Priority date	Apr 21, 2017
Publication date	Jan 30, 2020
Grant date	—

Abstract

The invention relates to a method for zinc phosphating components so as to form layers, said components comprising surfaces made of steel with a high tolerance against aluminum dissolved in the zinc phosphating bath, wherein the precipitation of poorly soluble aluminum salts can be largely prevented. In the method, a process is used of activating the zinc surfaces by means of dispersions containing particulate hopeite, phosphophyllite, scholzite, and/or hureaulite, wherein the proportion of particulate phosphates in the activation process must be adapted to the quantity of free fluoride and dissolved aluminum in the zinc phosphation.

First claim

What is claimed is:

1 . A method for the anti-corrosion treatment of a series of metal components, the series comprising components that have, at least in part, iron surfaces, in which method the metal components of the series successively undergo the following wet-chemical treatment steps:
(I) activation by contacting the metal components with an alkaline aqueous dispersion that has a D50 value of less than 3 μm and the inorganic particulate constituent of which comprises phosphates, the entirety of these phosphates being composed at least in part of hopeite, phosphophyllite, scholzite and/or hureaulite; (II) zinc phosphating by contacting the metal components from step (I) with an acidic aqueous composition containing
(a) 5-50 g/l of phosphate ions,
(b) 0.3-3 g/l of zinc ions,
(c) at least 15 mmol/kg of aluminum ions in dissolved form, and
(d) at least one source of fluoride ions,
wherein the concentration of phosphates in the form of particulate phosphate in mmol/kg, calculated as PO 4 in the alkaline aqueous dispersion, is greater than seven hundredths of the following term in mmol/kg:

[
AI
]

2

3


[

A



I

]

+

[
F
]

·

(

1
+

10

3.12
-
pH

)

(

Eq
.


1

)

[Al]: concentration of aluminum ions in dissolved form in mmol/kg
[F]: concentration of free fluoride in mmol/kg
pH: pH of the acidic aqueous composition of the zinc phosphating

2 . The method according to claim 1 , wherein the proportion of phosphates based on the inorganic particulate constituents of the alkaline aqueous dispersion of step (I), is at least 30 wt. %, calculated as PO 4 .

3 . The method according to claim 1 , wherein the proportion of zinc in the inorganic particulate constituent of the alkaline aqueous dispersion of step (I), is at least 20 wt. %.

4 . The method according to claim 1 , wherein the proportion of titanium in the inorganic particulate constituent of the alkaline aqueous dispersion of step (I), is less than 5 wt. %.

5 . The method according to claim 1 , wherein the amount of phosphates from the inorganic particulate constituent of the alkaline aqueous dispersion of step (I), is at least 40 mg/kg, calculated as PO 4 and based on the dispersion.

6 . The method according to claim 1 , wherein the pH of the alkaline aqueous dispersion of step (I), is greater than 8, but less than 12.

7 . The method according to claim 1 , wherein, in the acidic aqueous composition of the zinc phosphating, the total concentration, in mmol/kg, of sodium and/or potassium ions in dissolved form is less than the number 40 divided by the third root of the concentration of aluminum ions in dissolved form.

8 . The method according to claim 1 , wherein the concentration of aluminum ions in dissolved form in the acidic aqueous composition of the zinc phosphating is greater than 30 mmol/kg, but less than 100 mmol/kg.

9 . The method according to claim 1 , wherein the concentration of free fluoride is at least 2 mmol/kg, but not greater than 50 mmol/kg.

10 . The method according to claim 1 , wherein the pH in the acidic aqueous composition of the zinc phosphating is greater than 2.5, but less than 3.5.

11 . The method according to claim 1 , wherein neither a rinsing nor a drying step takes place between the activation and the zinc phosphating.

12 . The method according to claim 1 , wherein within the series, components that have aluminum surfaces and/or components that have aluminum surfaces in addition to the iron surfaces are also treated.

13 . The method according to claim 12 , wherein each component of the series is of the same composition and the pickling rate of aluminum based on the surface area of each component in the zinc phosphating is not greater than:

0.27
·

A
100



gm

-
2

(

Eq
.


2

)

A: actual drag-out from the zinc phosphating bath indicated in milliliters of the acidic aqueous composition per component and per square meter of the component.

14 . The method according to claim 12 , wherein each component of the series is of the same composition and the pickling rate of aluminum based on the surface area of each component in the zinc phosphating is greater than:

0.27
·

A
100



gm

-
2

(

Eq

Assignees

• Henkel Ag & Co Kgaa

Inventors

• Brouwer Jan-Willem
• Pilarek Frank-Oliver
• Resano Artalejo Fernando Jose
• Kroemer Jens
• Hamacher Matthias
• Balzer Marc

Classifications

• C23F11/188 Primary

  containing phosphates · CPC title

• C23C22/78 Primary

  Pretreatment of the material to be coated · CPC title

• C23C22/362 Primary

  containing also zinc cations · CPC title

• C23C22/73

  characterised by the process · CPC title

• C23C22/365

  containing also zinc and nickel cations · CPC title