JPS60145380A - Ni plated steel sheet having excellent corrosion resistance - Google Patents

Abstract

PURPOSE:To produce an Ni plated steel sheet with which pitting corrosion arises hardly and which is highly resistant to corrosion by subjecting successively a steel sheet incorporated with a specific ratio of C, solAl and Cu in Fe to Ni plating and formation of a chromate film. CONSTITUTION:A steel sheet contg. <=0.10% C, 0.005-0.08% Sol. Al and 0.05- 0.3% Cu and consisting of the balance substantially Fe is pretreated and is then electroplated with Ni. The plating is accomplished at about 3-300A/dm<2> current density, about <=80 deg.C plating temp. and about 150-1,500mg/m<2> plating weight. After the residue of the plating bath is removed from the surface of the steel sheet, a chromate film is formed thereon at about 3-30mg/m<2> in terms of metallic Cr in a plating bath prepd. by adding SO2<2-> ion and F<-> ion, etc. to an aq. soln. of chromic acid anhydride, etc. The steel sheet having excellent corrosion resistance as a blank material for a vessel is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) This invention relates to a Ni-plated intermediate plate which has excellent corrosion resistance and has a small amount of Fe eluted from pinhole defects in the N1-plated layer.

(Prior Art) In recent years, plated steel sheets have been increasingly used in beverage cans, for example, by welding can manufacturing methods, taking advantage of their excellent corrosion resistance, weldability, and excellent appearance and properties after painting. .

However, beverage cans are often used with any kind of content, which can cause problems, such as highly acidic contents and (J-). This tends to increase the amount of JFe eluted from the contents when used as a material for can manufacturing or other container materials. There is a demand for a Ni-plated steel sheet with low corrosion resistance and excellent corrosion resistance.

Generally, N]gold metal has corrosion resistance, but in a corrosive environment, it is significantly more cathodic (potentially noble) than the plated original plate (steel plate), so the corrosion current between the Ni gold metal and the plated original plate is large. Therefore, in order to reduce the number of pinholes in the N1 plating layer, it is necessary to improve the plating method or to
Measures to reduce pinhole defects have been taken, such as in Japanese Patent Laid-Open No. 84929 and Japanese Unexamined Patent Publication No. 51-151635, in which the N1 plated surface is treated with chromate. Even if it is possible to significantly reduce pinholes by painting the N] plating after chromate treatment, it is difficult to eliminate them completely, and also, machining scratches may occur during can manufacturing, exposing the steel surface. As a result, in a corrosive environment, a local battery is generated between the N1 metal and the exposed iron surface, and the plated original plate becomes anodic (
(potentially base), and a large amount of Fe elutes, particularly causing pitting corrosion.

(Structure, operation, and effects of the invention) In view of the above, the present inventors have carried out actual commercial production with the aim of providing an N1 plated steel plate that is resistant to pitting corrosion and has excellent corrosion resistance. It has been discovered that the desired steel plate can be obtained by adjusting the steel composition to bring the potential of the original plated plate (steel plate) closer to the blue direction (cathodicization).

The present invention was constructed based on this knowledge, and the gist thereof is: C: 0.10% or less, so]-AA: 0.005-
This is an N1-plated steel plate with excellent corrosion resistance, which is obtained by applying N1 plating or further chromate coating to a steel plate containing 0.08% Cu, 0.05 to 03% Cu, and the remainder being substantially Fe.

The present invention will be explained in detail below.

The molten steel melted in a converter, electric furnace, etc. is made into a slab through continuous casting method, ingot making, or blooming method, hot rolling, cold rolling, and annealing process, C: 0.10% or less 3- or less, 5olAF: 0.005-0.08%, Cu:
A plated original plate containing Fe in an amount of 0.05 to 03% with the remainder substantially consisting of Fe is manufactured. As the C content increases, the workability of the steel sheet deteriorates, and a large amount of cementite precipitated scattered on the surface of the steel sheet causes many pinholes to occur on the surface after N1 plating. Therefore, C component 7,1 is a harmful element that deteriorates corrosion resistance, and it is preferable to have a small amount t L <
, the upper limit was set at 0.10%. Aei is a deoxidizing element for molten steel, but it remains in the manufactured steel sheet], AP
If i$y is less than 0,005%, the incidence of surface defects due to oxygen gas will be significantly reduced, many pinholes will occur on the Nj plated surface, and the corrosion resistance will deteriorate.

Excessive S○, iAp, exceeding 0.08% is AQ.
, many oxides are scattered on the steel surface, causing unplated areas or 1-inch pinholes, and the integrity of the plating is lost.
Deteriorates corrosion resistance. Therefore, the so contained in the steel]
, Al4 is 0 as the amount that can stably ensure corrosion resistance.
Limited to those in charge of '00.5-008.

The addition of Cu brings the potential of the steel sheet exposed to a corrosive environment closer to the noble direction and closer to the potential of Ni, thereby improving the corrosion resistance of the steel sheet itself. In today's current steel plate technology for carbonated beverage cans, increasing the content of Cu does not have any effect on internal corrosion, but it does degrade the rust resistance of the external surface of the can. -It is said to me. This is thought to be due to the increase in the number of local batteries in corrosion due to the increase in Id- and Cu content, and it is necessary to keep the content low, and it is unavoidably mixed in during normal steelmaking operations.

The amount is kept to a minimum. Table 1 shows the measurement results of the immersion potential, corrosion loss, and corrosion current when N1 plating was applied to different Cui No. steel plates.

5- Unexamined Japanese Patent Publication No. 145380 (3) 0
．． By adding 0.05% or more, preferably 0.10% or more, the corrosion resistance of the Ni-plated steel sheet is significantly improved. However, if the amount added exceeds 0.3%, surface cracks will occur due to hot brittleness during the hot rolling process, so it is not desirable, and due to regulations from the manufacturing perspective of steel sheets, the upper limit is 0.3%, preferably. It was regulated to below 0.25 section.

The plated original plate manufactured with the above component composition is subjected to conventional plating pre-treatments such as degreasing and pickling, and electrolytic NJ plating is applied, but a conventional nickel plating method may be used.

The composition of the N1 plating bath, plating conditions, etc. are not particularly specified, but the current density is generally 3 to 300 A/dJ, and the plating temperature is 80° C. or less. An example of the addition of the N1 plating bath and the plating conditions are as follows.

(1) Plating bath composition: NiSO4.6H, Oz40
y/l, old C12・6H,,030f//l, H3B
O330? / Current density: 15A/dt = 7 = Bath temperature ゛ 40℃ N] Plating amount: 0.50 f /ly + 2 (2) Plating bath composition, nickel sulfamate 300f//1H
3B○3 25f//=%t R density,' 100 A/dm2 Bath temperature:
60℃ Plating amount; koOf/n? .

In addition, Ni-plated steel sheets are often used as materials for containers or can lids manufactured by a can-making method using a welding method, and are often used after being painted.

When painting is applied directly to a plated steel plate ((, N)
1 Due to the oxide film that forms on the plating surface, the adhesion of the paint, especially the corrosion resistance after painting, is extremely poor. Therefore, following N1 plating, after removing the residue of the 1st plating bath on the surface by washing with water, chromic anhydride, chromate (ammonium chromate, sodium chromate, etc.) or dichromate (ammonium dichromate) The method is carried out using a mixed aqueous solution of one or two types of I'J, dichromic acid nodah, etc., and an aqueous solution to which so, -2 ions, F- ions, etc. are added.

8- Although the treatment bath or treatment conditions for this chromate treatment are particularly specified, for example, the treatment is carried out under the following chromate bath and chromate conditions: (1) Chromate bath composition:
60 f/1Cr03-0.3 fl/l SO2-
2 Current density: 10 A/d m2 bath depth:
55℃ Chromate coating amount (metal Cr equivalent): 7.5 my/
yt? The N1-plated steel sheet manufactured with the above-mentioned composition or the chromate-treated steel sheet after N1 plating has a remarkable improvement in corrosion resistance due to the improved corrosion resistance of the plated original sheet (steel sheet) itself and the approach of the potential to the N1 plating layer.

In other words, the potential difference and current value decrease in the local battery generated between the N1 plating layer and the F4 protrusion such as the eaves caused by pinholes and processing after painting the plating layer and the chromate treatment film, and corrosion of the steel itself. By reducing the speed, the amount of Fe eluted from defective areas is significantly reduced, and the risk of pitting corrosion in exposed Fe areas is significantly reduced, resulting in a remarkable improvement in corrosion resistance.

Although the present invention has mainly been described with respect to improving the openness of N1-plated steel sheets used as a material for containers, it may also be used in other applications, such as improving the size of N1 plating or chromate treatment as a material for fuel containers containing alcohol. There is no question that it also applies when used as a term.

Therefore, when used as a container material, Ni
The amount of plating is generally 150~]-50o+w, the amount of ridge romate coating is 3~30 mq/d in terms of metal Cr,
For fuel containers, the amount of N1 plating is 20 to 6o7/d, and the amount of chromate film is 20 to 80 m9/d in terms of metal Cr, but in the present invention, (Cl, amount of Ni plating,
The amount of chromate coating is not specified, and the amount of coating may be set depending on the application.

As described above, the present invention is applicable to all N1 plated steel sheets whose original plate composition has been determined or chromate-treated steel sheets after N1 plating. It goes without saying that when used as a material for containers that generate a large amount of holes, it exhibits the effect of improving capital resistance.

Next, in the steel composition Oki, C,5olAp,,C
Although the content of u10- is specified, it is included as an unavoidable impurity in the steel manufacturing process at the current industrial level.
It is natural that such things are included.

Similarly, a case where Co, S, etc. contained as inevitable impurities are included in the N1 plating layer is also included in the scope of the present invention.

(Example) Examples of the present invention will be described below.

(1) Using steel with added Co added as shown in Table 2, after performing pre-treatments such as degreasing and pickling that are usually carried out in electroplating, N1 plating (500 m
q/m2) and chromate treatment by CrO3-5o4-2 cathodic electrolytic treatment (Cr adhesion t'7 m9/J)
The results of a corrosion resistance test for beverage can containers on plated steel sheets, uncoated sheets and painted sheets are shown below.As comparative materials, aluminum killed steel without Cu added and The corrosion resistance of N1 plated steel plate using rimmed steel was shown.

(2) Table 3 shows the addition of Cu when the amount of Cu added is changed. Showa GO-145380 (7), ξ ≦ Peeling S (JT'UO 薇・(n[o 米×, QO
8f! /), 2) were performed.

The results of a corrosion resistance test conducted on a fuel tank containing alcohol by square cylinder drawing using N1-plated steel sheets are shown.

As a comparative material, the corrosion resistance of N1-plated steel sheets was shown using aluminum-killed steel with added Cu and killed steel with T1 addition.

As shown in the examples above, the N1-plated steel sheet using the Cu-added steel sheet of the present invention can exhibit extremely excellent corrosion resistance performance due to the proximity of the potential of the N1-plated original plate and the improved corrosion resistance of the plated original plate. it is obvious.

Agent: Patent attorney Yasushi Yoshishima

Claims (1)

[Claims] C: 0 Co-O section or below, 5olAij: 0.005~
N1 Metsuki Rin is characterized by its excellent corrosion resistance, which is characterized by Ni plating or further chromate coating applied to a steel plate containing O○8%, Cu: 0.05 to 03, and the remainder being substantially Fe. board