JPH0472097A - Electrolytic cleaning method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention The present invention relates to an electrolytic cleaning method, in which metal plates are appropriately colored when they are cleaned with an electrolytic solution containing a Si-containing detergent such as sodium orthosilicate. The aim is to prevent this from happening.

(Industrial application field) Cleaning processing technology for metal plates in electrolytic cleaning lines used for continuous annealing, hot plating, electroplating, or before painting.

(Prior art) Electrolytic cleaning of metal plates such as steel plates has been carried out in the electrolytic cleaning line (ECL) for a long time. Efforts are made to ensure cleanability. That is, for example, when the line speed is high (200 mpm or more), the electrolytic current is increased in proportion to the speed so as to keep the current density constant, but when the line speed is low (200 mpm or less), cleaning performance is given priority and the electrolytic current is increased. It is implemented by setting the current to a constant value such as 2500A.

In addition, in such an electrolytic cleaning line, sodium orthosilicate (NazllnSiO4) and sodium metasilicate (NazllnSiO4) are used.
SiOs 45HzO) etc. are used.

(Problems to be Solved by the Invention) In the conventional techniques as described above, coloring may occur on the metal plate when the line speed is low.

For example, coloring may be observed in mild steel materials at low speeds such as 30 mpm or less.

It is easy to conclude that such coloring is caused by oxidation, but according to the results of the inventors' study of manufacturing tests and SUS rolling tests of 36% Ni-Fe amber materials, it should be more resistant to rust than mild steel materials. Coloration is observed in these coils, which inevitably becomes a problem in materials that are subject to priority management.

That is, in any case, with the above-mentioned conventional techniques, it is not possible to stably produce a metal plate with good surface quality, and the yield is also reduced.

"Structure of the Invention" (Means for Solving the Problems) The present invention was created after repeated studies to solve the problems of the conventional products as described above. When cleaning with an electrolytic solution containing 2 to 10% by weight of sodium silicate, the electricity density is 16.5 q / d.
This is an electrolytic cleaning method characterized by preventing coloring of the plate surface by keeping the temperature below m2.

Function Sodium silicate is 2 to 10% by weight of metal plates such as cold-rolled steel plates.
Appropriate cleaning is performed by cleaning with an electrolytic solution.

During the electrolytic cleaning, the electricity density was set to 16.5 q/
By keeping the temperature below d+w'', coloring on the plate surface can be effectively prevented even under relatively slow processing conditions where an effective cleaning effect is ensured.

The present invention is equally applicable to continuous annealing, hot-dip plating, electroplating, electrolytic cleaning treatment before painting, etc.

(Example) To explain a specific embodiment of the present invention, when electrolytically cleaning a cold rolled steel sheet as a pretreatment for a stress relief and bright annealing line in a thin sheet production facility, a sodium silicate concentration of 3% was used. Orthosilicic acid solution is used as electrolyte,
When the surface properties of the plate were investigated when the plate was passed through the first and second electrolytic rolls installed in the electrolytic cell and subjected to electrolytic treatment at a speed of 10 mpm or less, which increases the cleaning effect, the degree of cleaning was good. However, as the electrolytic current increases, the plate surface becomes colored and the concentration gradually increases.

In other words, as a result of repeated consideration of such results, 101I
At low speeds such as lpI11 or less, cleaning performance is good regardless of the electrolytic current value (charge density), and tape tests show that there is a difference of about 4% in reflectance between the front and back sides of the board (the back side has high cleaning performance). ), it was confirmed that there was no difference in cleaning performance. However, when the current density increases during such electrolytic cleaning, coloration is observed, and we investigated the coloration of the plate under the assumption that it was Fe oxide caused by electrolysis, and conducted a single electrolytic test to confirm this. I tried to do it, but the electrolysis was 0.
No iron oxide due to No. 1 could be observed.

Therefore, in order to investigate the actual state of such coloring, we performed an Auger analysis on the central part of each test piece and found that Si was detected in the colored plates. I learned that it is controlled by the electric charge density during processing. That is, FIG. 1 summarizes these results and shows that when the charge density is 16 to 17 q
Si is detected when the temperature exceeds 76 m'', and this 5lffi degree increases rapidly in the range up to a charge density of 30 q 76 m'', and increases thereafter, but from 60 to 7 m''.
From about 0 q 76 m'', a low: $1 ftl direction is indicated.In addition, regarding the Si depth on the right vertical axis in Fig. 1, the Auger analysis method irradiates the material with an electron beam, and the Auger electrons coming out from there This method analyzes the extreme surface layer of the material surface by measuring the energy order and amount of the electron beam.Since the depth data from the plate surface that is approximately proportional to the time of electron beam irradiation is obtained, the irradiation time can be expressed as the Si depth. However,
In any case, the relationship is approximately proportional to the Si concentration.

Also, Figure 2 shows the relationship between the electric quantity density, current density, and line speed, and the electric quantity density is 16.5q.
It was confirmed that coloring occurred at temperatures above /dmt, and as the line speed decreased, the plate was colored due to Si adhesion, and when the current density was kept constant at 200 mpm or less as in the conventional technology, coloring did not occur. There is no choice but to make it highly likely.

Specific operational examples of the present invention based on these results are as follows:
It is as follows.

Operation example 1 When electrolytically cleaning a continuously annealed soft steel plate using an electrolytic solution containing 3 wt% of sodium orthosilicate, the line speed was set to 10 mpm and the electricity density was set to 10 q /
As a result of the cleaning treatment using an electrolytic current of 100 dm'', it was possible to obtain a cleaned mild steel plate with no coloration.

Operation example 2 A steel plate for hot-dip plating was washed at a line speed of 8 m in an electrolytic cleaning facility using the same electrolyte as in operation example 1.
During electrolytic cleaning at pm, the electricity density Oq/dIIl!
As a result of the cleaning treatment using an electrolytic current of 1, a good cleaning original plate for plating without coloring could be obtained.

Operation example 3 Amber material of 36% N1-re was cleaned with the same electrolytic solution as in operation example 1.2 at a low speed of 10 mpm, and when carried out at a charge density of 5 q/dm, no coloration was observed. On the other hand, when the charge density was set to 20 q/dm'' under the same conditions as above, coloration due to 5isC was observed.

"Effects of the Invention" According to the present invention as explained above, the cause of coloring on the surface of a metal plate when electrolytically cleaning a metal plate using a detergent containing Si is clarified, and the coloring due to the adhesion of St can be rationalized. This invention is industrially very effective because it prevents this from occurring, makes it possible to stably obtain plates with good surface properties through appropriate cleaning, and improves the yield.

[Brief explanation of drawings]

The drawings show the technical contents of the present invention, and FIG. 1 is a diagram summarizing the relationship between the current density, the amount of Si deposited, and the coloring state of the metal plate to be treated, and FIG. 1 is a diagram summarizing the relationship between line speed, current density, charge density, and whether or not a metal plate to be treated is colored for the technology of FIG. No. 2 Enden Hiroshi J g, 7tW 2λn Qnp Deng

Claims (1)

[Claims] When cleaning a metal plate with an electrolytic solution containing 2 to 10% by weight of sodium silicate, the electricity density was set to 16.5 q/dm.
An electrolytic cleaning method characterized by maintaining the temperature at ^2 or less and preventing coloring of the board surface.