DD270092A1 - METHOD FOR THE CHEMICAL TREATMENT OF METAL PARTS - Google Patents

Abstract

The invention relates to a method for the chemical treatment of metal parts of preferably iron materials in a chromic acid solution prior to the hot dip metallizing, in particular before the hot dip aluminizing. The treatment is carried out between surface cleaning and hot dip metallizing to ensure and improve wetting ability. The metal parts are purified according to methods known per se to the state "metallically pure" in a chromic acid solution with the parameters 3 ... 45 g / l CrO3, min. 0.06 g / l Cr3 ions and min. 0.04 g / l Fe3 ions dipped at a temperature of 310 ... 355 K for at least 60 seconds and dried at a temperature of at least 350 K.

Description

Title of the invention Process for the chemical treatment of metal parts Field of application of the invention

The invention relates to a method for the chemical treatment of metal parts of preferably iron materials in a chromic acid solution before the sohmelt dip galvanizing, in particular the hot dip aluminizing. This treatment is carried out between surface cleaning and hot-dip metallizing to ensure and improve wettability,

^v Characteristic of the known technical solutions

It is known that metal parts to obtain a protective coating by Schmelztauchmetallisisrung, pure metallic se: .η need and must be subjected to increase the wetting ability with the tongue _(the metal melt of a separate chemical treatment.

Among other things, it is known to treat metal parts in chromic acid solutions before hot dipping processes. Thus, from DD-PS 223 730 a method for Tauchaluminieren known. With this invention, products of iron and its surface-cleaned alloys are dipped in a chromium / sodium hydride solution, then rinsed in water and placed in a heated sodium tetraborate solution, then dried and fed to the bath with molten aluminum. Although the application of the process is possible, the quality of the aluminum dust achieved is unstable, making industrial application unacceptable.

Object of the invention

The object of the invention is to design the method of chemical treatment for hot-dip metallization in such a way that stable quality parameters of the metal protective layers are achieved by securing and improving the wetting ability of the metal parts relative to the melt.

Explanation of the essence of the invention

It is an object of the invention to make the method so stable that the resulting in industrial hot dip metallizing of chemically treated by the prior art metal parts resulting protective layers meet the technical standards.

According to the invention the object is achieved in that the metal parts whose surface is cleaned according to the known per se method to the state "metallically pure" in a chromic acid solution with the parameters

3 ... 45g / l CrO ₃

q +

min. 0.06 g / l Cr ions at least 0.04 g / l Fe ³⁺ ions

at a temperature of 31O ... 355K at least 60sec. dipped and dried at a temperature of at least 350K. The concentration of the Cr and Tr ³⁺ ions of the freshly prepared chromic acid solution can be achieved by chemical reaction of metal parts of unalloyed or low-alloy steel with the solution, or in the case of a new batch of the chromic acid solution proportionately already used solution can be added.

Ausführungsb games

Based on embodiments, the inventor will be explained in more detail.

Example 1:

The metal parts, the surface of which has been cleaned to a "metallically pure" state, are immersed in a chromic acid solution whose concentration of Cr ³⁺ and Fe ³⁺ ions is formed by chemical reaction of iron material with the treatment solution, of the following composition:

4.0 g / l CrO ₃

0.25 g / l Cr ³⁺ ions 0.14 g / l Fe ³⁺ ions

Solution temperature: 323 K Dive time: 270 s

Dry temperature: 360 K

Example 2:

The pretreated according to Example 1 metal parts are in a chromic acid solution with

10.0 g / l CrO ₃ immersed. The concentration of

0.15 g / l Cr3 ⁺ ions and 0.04 g / l Fe ³⁺ ions

is achieved by the addition of an equivalent amount of a treatment solution already used.

Solution temperature: 310 K Dive time: 90 s

Drying temperature: 375 K

Claims (3)

1 "process for the chemical treatment of metal parts of preferably Elsenwerkstoffen in a Chromäurelöeung before the Schmelztauchmet · -jllisierung, characterized in that the metal parts with a metallically pure upper surface in βΛηβ solution with the parameters cA CrO ₃ at least 0.06 g / l Cr3 + ions
at least 0.04 g / l Fe ³⁺ ions at a temperature of 31O ... 355Kmind. Dipped for 60 seconds and at a temperature of low. To be dried 350K, -1- claims 2. The method according to claim 1, characterized in that the concentration of Cr and Fe ions is achieved by chemical reaction of Eisenwerketoffen with the prepared chromic acid solution. 3, Method according to claim 1, characterized in that in the new batch of chromic acid solution proportionately already used solution is added.