GB2041241A

GB2041241A - Zinc plated steel plate and can produced from the same

Info

Publication number: GB2041241A
Application number: GB7903847A
Authority: GB
Original assignee: Nisshin Steel Co Ltd
Current assignee: Nippon Steel Nisshin Co Ltd
Priority date: 1979-02-02
Filing date: 1979-02-02
Publication date: 1980-09-10
Also published as: GB2041241B

Abstract

A zinc plated steel plate at least one surface of which is substantially free from oxides and coated with an anti-rust film, and a can produced from such zinc plated steel plate and having an interlocking seam joint bonded by soldering.

Description

SPECIFICATION Zinc plated steel plate and can produced from the same This invention relates to a zinc plated steel plate having an improved solderability, and also to cans such as 18 litre-cans, paint cans and oil cans which are produced from such zinc plated steel plate using ordinary soldering techniques.

Heretofore, a tin-plated steel plate (hereinafter referred to as "tinplate") has been used as a starting material to produce various cans by the use of solder. However, recently tin resources have started to become exhausted world-wide and the price of tinplate has risen. Accordingly, the development of other starting materials having satisfactory solderability and anti-corrosive properties which are as good as those of tinplate is in high demand.

In order to satisfy this demand, a steel plate having a thin metallic chromium layer and chromic acid film, i.e. a tin-free steel plate, has been developed and used as a starting material to produce cans. This tin-free steel plate has the same or better anticorrosive properties and paintability for baking paint and its price is lower in comparison with tinplate.

However, the solderability of this plate is much poorer than that of tinplate, which is a great disadvantage. Therefore, when manufacturing cans using the tin-free steel plate, it is necessary to employ a seam welding technique or other special bonding techniques using a bonding agent such as seam cement on its bonding counterpart.

On the other hand, in order to produce cans on a mass production scale, an operating efficiency and production efficiency equivalent to those in the pre senttinplate can producing process are required, and complete soldering must be carried out by can producing equipment using the present automatic soldering system. The above-mentioned seam welding technique or other special bonding techniques employed to produce cans from the tin-free steel plate is poorer with respect to working efficiency, production efficiency and cost than the conventional soldering technique, and also creates various problems with respectto production equipment.Under these circumstances, the development of new and cheap can materials is desired, which do not give rise to the above-mentioned various problems as in the case of the bonding of tin-free steel plate, and which can be substituted for conventional tinplate.

The present invention in one aspect provides a zinc plated steel plate at least one surface of which is substantially free from oxides and coated with an anti-rust film.

The invention in another aspect provides a can produced from zinc plated steel plate according to the first aspect of the invention, the can having an interlocking seam joint bonded by soldering.

It has been found that a zinc electroplated steel plate, a zinc vapour deposited steel plate, or a galvanized steel plate plated by the use of a molten zinc plating (galvanizing) bath containing easily oxidizable elements such as aluminium, having an improved solderability by making the surface substantially free from oxides and coating an anti-rust film on the oxide-free surface, is an excellent can material. The zinc plated steel plate thus treated has a solderability equivalent to that of tinplate, and has a better corrosion resistance and is cheaper than tinplate.

It is envisaged that the zinc plated steel plate according to the invention will be widely used not only as a starting material for cans but also for various other uses where appropriate solderability is required, for example, chassis of light electrical applicances such as radios and televisions.

In the following description reference will be made to the accompanying drawings, in which: Figures la, 1b and 1c are cross-sectional views showing the state of penetration of solder into respective interlocking seam joints of (la) zinc plated steel plate of this invention having an improved solderability, (ib) comparative ordinary galvanized steel plate and (inc) ordinarytinplate prepared in accordance with the procedures in Example 6 below;; Figures 2a, 2b and 2c are cross-sectional views showing the state of penetration of solder into respective interlocking seam joints of body plates of 18 litre-cans produced from (2a) zinc-plated steel plate of this invention having an improved solderability, (2b) comparative ordinary galvanized steel plate, and (2c) ordinarytinplate prepared in accordance with a commercial tinplate can production line as described in Example 7 below; Figure 3 is a graph showing a curve illustrating the relation between retention time (sec) and solder spread area (mm2) with regard to the zinc-plated steel plate of this invention, where tan a = Initial Spreading Rate (mm2/sec), and Se = Equilibrium Spread Area (mm2); and Figure 4 is a graph showing curves illustrating the relation between the secondary ion intensity ratio (I,; +11on +) and solder initial spreading speed (mm2/sec) or the solder equilibrium spread area after 30 seconds (mm2).

The expression zinc plated steel plate substantially free from oxides on its surface used herein means plate having a surface (up to a depth of 200 Angstroms) wherein the ratio of aluminium ion detection intensity (IA +)/zinc ion detection intensity (lzn +) is not higher than 20 (IA + /Izn + = not higher than 20).

These values of aluminium ion detection intensity and zinc ion detection intensity are the values determined by an ion Microanalyzer (Hitach IMA-2 Type) under the following conditions: Primary Ion Ar+ Accelerated Voltage 15 KV Sample Electric Current 0.3 ,aA Primary Ion Beam Diameter 500 zm We have discovered that a zinc plated steel plate substantially free from oxides on its surface, i.e. zinc plated steel plate having a surface wherein the ion The drawings originally filed were informal and the print here reproduced is taken from a later filed formal copy.

intensity ratio (IA + /IZn +) is not higher than 20, has an excellent solderability. That is, as shown by Figure 4, zinc plated steel plate having a surface with an ion intensity ratio of not higher than 20 has a solder initial spreading speed (mm2/sec) of not less than 9 and a solder equilibrium spread area after 30 seconds (mm2) of not less than 60, which are the essential conditions for commercially acceptable solderability.

If a steel plate is plated in a zinc-aluminium bath containing 0.1-0.3% by weight of aluminium generally used in continuous molten zinc plate (galvanizing) lines, oxides other than zinc oxide, mainly aluminium oxide, are formed on the surface layer. In addition to aluminium oxide, oxides of easily oxidizable elements such as titanium, chromium, silicon and iron may be possibly formed either alone or in a composite form as spinel type oxide; however, the amount of oxides other than aluminium oxide is very small and their influence on solderability is negligible. If these stable oxides comprising aluminium oxide as the main component are present on the surface, they interrupt activation by flux during soldering, and consequentlythe solderability of ordinary galvanized steel plate is poor. As discolsed in Japanese Laid Open (Kokai) Patent Application No.

51-95941, if these oxides on the surface are removed by etching, the solderability is notably improved.

However, if these oxides are not present on the surface, the surface of the plate is active and not corrosion-resistant. Therefore, zinc white rusts of, for example, carbonates and hydroxides are easily formed on the surface simply by placing the plate outdoors, and the plate becomes useless.

The zinc-plated steel plate of this invention does not have the above-mentioned disadvnatages. The zinc-plated steel plate of the invention may be prepared by electro-plating, vapour depositing or galvanizing in a molten zinc plating bath including easily oxidizable elements such as aluminium in a well known manner. According to this invention, the solderability and anti-corrosion properties of the zinc plated steel plate are improved by making the plate substantially free from oxides and coating an antirust film on the oxide-free surface to keep the surface substantially free from oxides.In the case of a zinc electroplated or zinc vapour deposited steel plate, an etching process is not necessary before coating an anti-rust film since the plate is substantially free from oxides as it is, but in the case of galvanized steel plate an etching process is required to remove oxides derived from the plating bath.

A zinc-plated steel plate having its surface substantially free from oxides and coated with an antirust film has a solderability equivalent to or higher than that of tinplate, and therefore it can be fabricated into cans using a conventional tinplate can producing line with the same or higher working efficiency and production efficiency as in the production of conventional tinplate cans. In addition to this advantage, the zinc plated steel plate cans of this invention have a higher corrosion resistance and durability than conventional tinplate cans. Substantially most of the oxides on the surface of the zinc plated steel plate can be removed by dipping the plate in an etching agent such as HCI, NaOH or other commercially available etching agents for a short time or by spraying the etching agent onto the plate.

The plate thus treated or the plate having substantially no oxides on its surface and coated with an anti-rust film has excellent solderability.

The anti-rust film may be suitably composed of an acryl type resin, an alkyd type resin or a petroleum type wax as described in the following Examples.

The anti-rust film used in the present invention is preferably an organic anti-rust film. Examples of organic anti-rust films are as follows: (1) Acryl Type Resin, e.g. "CeBo HW-20" (trade name) manufactured byToyo Pharmachemical Co., Ltd.

Composition (% by weight): polyacrylic ester 20% isopropyl alcohol a minor amount non-ionic water the rest (2) Alkyd Type Resin, e.g. "Pipe Coat No. 692" (trade name) manufactured by Kansai Paint Co., Ltd.

Composition (% by weight): alkyd resin varnish 44% petroleum type resin varnish 9% drying agent 1% thinner 46% (3) Petroleum Type Wax, e.g. "Non RusterPSW-51" (trade name) manufactured by Yushiro Chemical Industry Co., Ltd Composition (% by weight): high melting petroleum type wax 15-17% low melting petroleum type wax 8-10% hard synthetic wax 10-12% higher aliphatic acid amine soap 3-4% antiseptic agent a minor amount water 60-65% The invention will be further described with reference to the following illustrative Examples.

Example 1 Ordinary minimized spangle or extra smooth galvanized steel plate having a plate thickness of 0.32 mm and an amount of zinc on one side of about 60 g/m2 plated continuously in a molten zinc plating bath containing a minor amount of aluminium and subjected to skin pass rolling was spray-treated with a 15% by weight solution of commercially available alkali type etching agent (trade name, "NP Cleaner No. 10SF" manufactured by Nippon Paint Co., Ltd., Composition: NaOH = 40%, surface active agent = a minor amount, and non-ionic water = the rest) at 80 C under a pressure of 0.5 kg/cm2to remove substantially most of the oxides on the surface (IA + /IZn + = 3), and was then coated with a 15% by weight aqueous solution of an acryl type resin (trade name, "CeBo HW-20" manufactured byToyo Pharmachemical Co., Ltd.) as an anti-rust film by means of a roll coater. The plate thus treated was dried at 100-150 C for about 1 minute. The dry plate was then investigated with regard to the relation of the thickness of the anti-rust film to solderability and anti-corrosion properties. The results are shown in Table 1.

TASLEl-Relation of Thickness of Acryl Type Resin Anti-rust Film to Solderability and Anti-corrosion Properties of Galvanized Steel Plate.

Anti-corrosion Solder Spreadability('' Properties Salt Thickness Initial Water of Spreading Equilibrium Wetting Spraying Anti-rust Speed Spread Area Test'2-" Test Film (clam) (mm2/Sec) (mm2) Results Results 0 18 140 70%Wh ite 80%White Rust Rust 0.1 18 140 40-60% ,, 80% 0.3 18 140 15-30% ,, 70-80% 0.4 18 140 10-25% ,, 70-80% 1.1 18 138 5-10% ,, 60-70% 3.4 17 136 3-6 % ,, 45-55% 5.9 17 134 1-5 % ,, 40-50% 12.1 16 133 Normal 15-30% 15.8 16 130 Normal 10-20% 20.6 15 122 Normal 5-15% The tests were carried out in the following manner.

(1) SolderSpreadability A test sample of 50 mm x 50 mm was placed on a solder bath maintained at 280 C, and 0.2665 g of wire solder (rosin type flux cored wire solder having a dimaeter of 2 mm, Pb/Sn = 50/50) in the form of a ring was placed on the test sample. Thereafter, the spreading movement of the solder upon heating was measured. The solder spreadability of the test mater ial was evaluated by determining the tan a (initial spreading speed, mm2/sec) and Se (equilibrium spread area, mm2) after 30 sec. according to the sol der spread curve as shown in Figure 3.

121 Anti-corrosion Properties /2oil Wetting Test The anti-corrosion properties were evaluated by observing the state of rust on the surface of the test sample after placing the test sample under dew point conditions at a relative humidity of 98% at 500C for 50 hours.

(2oil Salt Water Spraying Test This test was carried out according to the JIS Z 2371 Salt Water Spraying Test, and the anticorrosion properties were evaluated by observing the state of rust on the surface of the test sample after 10 hours.

It was experimentally found that anti-corrosive zinc plated steel plate which can be satisfactorily produced into various cans such as 18 litre cans, paint cans and oil cans and chassis for light electrical apparatuses such as radios and televisions should preferably satisfy the following conditions.

Solder Spreadability Initial Spreading Speed = not less than 9 mm2/sec.

Equilibrium Spread Area = not less than 60 mm2 Anti-corrosion Properties (2-i) Wetting test: The amount of white rust occurring on the surface after 50 hours is preferably not more than 30%.

(2-ii) Salt Water spraying test: The amount of white rust occurring on the surface after 10 hours is preferably not more than 80%.

As can be seen from Table 1, if the thickness of the anti-rust film is less than 0.3 the anti-corrison properties become poor and do not satisfy the above conditions. On the other hand, if the thickness of the anti-rust film exceeds 20 ijm, it becomes difficult to obtain an anti-rust film having a uniform thickness and this is not preferable from the economical view point although the solder spreadability and anticorrosion properties satisfy the above conditions.

Therefore, it was found that the thickness of an acryl type resin anti-rust film should preferably be 0.3-20 #m in view of solder spreadability, anti corrosion properties, uniform coatability and economy.

Example 2 A commercially available 15% by weight aqueous solution of an acryl type resin (Trade name, "CeBo HW-20" manufactured by Toyo Pharmachemical Co., Ltd.) was coated as an anti-rust film with a roll coater onto commercially availabe zinc electroplated steel plate defined as JIS G 3313 (lAl + llzn + = less than 0.1, the thickness of the plate = 0.6 mm, amount of zinc ahdering to one side = 20 gum2, not subjected to skin pass rolling and chemical conversion coating).

The plate thus coated was heated at 100-150 C for about 1 minute to dry.

The relation of the thickness of the dry anti-rust film to the solderability and anti-corrosion properties of the zinc electroplated steel plate was investigated.

The results are shown in Table 2.

TABLE 2-Relation of Thickness of Acryl Type Resin Anti-rust Film to Solderability and Anti-corrosion Properties of Zinc Electroplated Steel Plate

Anti-Corrosion Solder Spreadability Properties Salt Thickness Initial Water of Spreading Equilibrium Wetting Spraying Anti-rust Speed Spread Area Test Test Film (,am) (mmYsec) (mmq Results Results o 1 20 170 100% White 1-3% Red Rust Rust 0.2 20 170 80-100% " Small Dotty Red Rust 0.5 20 170 20-35% ,, 80-100 S White Rust 1.0 19 166 1025% ,, 6580% 3.7 19 160 410% ,, 55-70% 6.2 18 152 16 % " 50-60% 11.6 18 149 1-2 % ,, 2540% 17.3 16 137 Normal 20-30% 22.1 16 128 Normal 10-25% The above tests were carried out in the same manner as in Example 1.In view of the conditions of suitable solderability and anti-corrosion properties as described in Example 1, it was found that the thickness of the acryl type resin anti-rust film on zinc electroplated steel plate should be preferably at least 1.0,am. On the other hand, if the thickness exeeds 20 ,um, the plate may become impractical for the same reasons as described in Example 1.

Example 3 A commercially available 15% by weight aqueous solution of an acryl type resin (trade name, "CeBo HW-20" manufactured by Toyo Pharmachemical Co., Ltd.) was coated as an anti-rust film with a roll coater onto commercially available zinc vapour deposited steel plate (IA + /IZn + = less than 0.1, the thickness of the plate = 0.6 mm, amount of zinc adhering to one side = 25 g/m, not subjected to skin pass rolling and chemical conversion coating). The plate thus coated was dried at 100-150 C for about 1 minute.

The relation of the thickness of the anti-rust film after drying to the solderability and anti-corrosion properties of the zinc vapour deposited steel plate was investigated in the same manner as in Example 2. The resuts are shown in Table 3.

TABLE 3-Relation of Thickness of Acryl Type Resin Anti-rust Film to Solderability and Anti-corrosion Properties of Zinc Vapour Deposited Steel Plate

Anti-corrosion Solder Spreadability Properties i Thickness of Spreading Equilibrium Wetting Spraying Anti-rust Speed Spread Area Film (am) (mm2/sec) (mm2) Results Results 0 19 160 100% White Small Dotty Rust Red Rust 0.2 19 160 80-100% ,, 100% White Rust 0.5 18 155 20-33% ,, 80-95% 1.0 18 150 10-25% ,, 65-80% 3.7 17 148 510% ,, 50-70% 6.2 17 145 1-5 % " 4555% 11.6 17 142 1-2 % " 2040% 17.3 15 135 Normal 15-25% 22.1 15 126 Normal 10-20% The testing methods were the same as in Exam ples 1 and 2.

In view of the conditions for suitable solderability and anti-corrosion properties as described in Exam ple 1, it was found that the thickness of the acryl type resin anti-rust film on zinc vapour deposited steel plate should preferably be at least 1.0,am. On the other hand, if the thickness exceeds 20,am, the plate may become impractical for the same reasons as described in Example 1.

Consequently, judging from the results of Examples 1, 2 and 3, it was found that the thickness of an acryl type resin anti-rust film should preferably be 1.0-20,am in view of solder spreadability, anti corrosion properties, uniform coatability and economy.

Example 4 An alkyd type resin (trade name, "Pipe Coat No.

692" manufactured by Kansai Paint Co., Ltd.) was coated as an anti-rust film with a roll coater onto the surface of galvanized steel plate from which sub stantially most of the oxides had been removed (IA + /Izn + = 4). The plate thus coated was heat-dried.

The relation of the thickness of the anti-rust film after drying to the solderability and anticorrosion properties of the molten zinc plated steel plate was investigated. The results are shown in Table 4.

TABLE 4-Relation of Thickness of Alkyd Type Resin Anti-rust Film to Solderability and Anti-corrosion Properties of Molten Zinc Plated Steel Plate

Anti-corrosion Solder Spreadability Properties Salt Thickness Initial Water of Spreading Equilibrium Wetting Spraying Anti-rust Speed Spread Area Test Test Film (clm) (mm2/sec) (mm2) Results Results Fil m (u m) ( mm2/sec) (m m2) Results Results 0.5 20 150 35-50% White 70-85% White Rust Rust 1.0 18 140 20.30 /O ,, 60-75% 4.3 18 140 10-25% ,, 50-70% 10.7 13 124 5-10% ,, 30-45% 15.0 9 80 1-5 % ,, 10-20% 21.1 ; 6 61 Normal 5-10% The testing methods were the same as in Example 1. In view of the conditions for suitable solderability and anti-corrosion properties as described in Exam ple 1 as well as the above results, it was found that the thickness of the alkyd type resin anti-rust film on molten zinc plated steel plate should preferably be 1.0-15,am.

Example 5 The same lot of commercially available galvanized steel plate as in Example 1 was spray-treated with the same commercially available alkali type etching agent as in Example 1 to remove substantially most of the oxides from the surface (IA + 11Zn + = 3), and was then coated with commercially available pet roleum type wax (trade name, "Non Ruster PSW-51" manufactured by Yushiro Chemical Industry Co., Ltd.) as an anti-rust film by means of a roll coater.

The plate thus treated was dried at room temperature for 48 hours. The relation of the thickness of the dry anti-rust film to the solderability and anticorrosion properties of the molten zinc plated steel plate was investigated. The results are shown in Table 5.

TABLE 5-Relation of Thickness of Petroleum Type Wax Anti-rust Film to Solderability and Anticorrosion Properties of Molten Zinc Plated Steel Plate

Anti-corrosion Solder Spreadability Properties Salt Thickness Initial Water of Spreading Equilibrium Wetting Spraying Spread SpeedSpreadArea film (clam) (mm2/sec) (mm2) Results Results 1.2 18 140 20-35% White 60-80% White Rust Rust 2.0 18 140 10-25% ,, 65-75% 5.5 18 140 5-10% ,, 50-70% 13.9 18 144 Normal Normal In view of the conditions for suitable solderability and anti-corrosion properties as described in Example 1 as well as the above results, it was found that the thickness of the petroleum type wax anti-rust film should be at least 2.0,am. On the other hand, if the thickness exceeds 20 clam, the plate may become impractical for the same reasons as described in Example 1.

Consequently, in view of solder spreadability, anti-corrosion properties, uniform coatability and economy, the thickness of a petroleum type wax anti-rust film should preferably be 2.0-20 m.

Example 6 Cans were prepared by means of an 18 litre can production line using general soldering techniques from the following plates: (a) a zinc plated steel plate (lAl + /IZn = 3) having an anti-rust film thickness of 1.1 ,um prepared as in Example 1; (b) ordinary galvanized steel plate chromated in an amount of about 20 mg/m2, from which oxides on the surface were not removed for the purpose of comparison; and (c) commercially available tin electroplated steel plate having a thickness of 0.32 mm, the amount of tin coated on one side being about 10 g/m2.

Generally, in the production of tin plate cans, an interlocking seam joint is bonded by means of the dip soldering or wire soldering method or a combination of the two methods on a large scale.

For the purpose of checking the solderability required for the can material with regard to the above three samples (a), (b) and (c), the penetrability of solder into a interlocking seam joint was investi gated in the following manner.

Two sheets of each of the above respective sam ples each having a size of 0.32 mm x 60 mm x 60 mm were prepared for this test. An interlocking seam joint having a constant clearance was pre pared by folding each end of the sample to a width of 5 mm and interlocking the folded ends by applying a load of 150 kg by means of an Amsler universal test machine.

One side of the joint was then coated with a brush with a water soluble flux having the composition below, and the sample was placed on a solder bath maintained at 280"C.

Composition of Flux ZnCI2 18% by weight NH4CI 12% by weight Non-ionic surface active agent 0.003% by weight Higher alcohol the rest Wire solder (diameter = 2.0 mm, Sn 40% by weight-Pb 60% by weight) was then speedily and uniformly plated along the whole length of the joint, and was uniformly heated for about 20 seconds. The sample was then cooled and washed with water to remove the remaining flux. The solder penetrability of the respective samples was evaluated by observing the appearance and the sectional shape of the joint part.

The results are shown in Figure 1. Thus, the appearance and the sectional shape of the interlock ing seam joint of (a), the zinc plated steel plate of this invention having an excellent solderability, were substantially equivalent to those of (c), the ordinary tin plate, and consequently it was shown that (a), the zinc plated steel plate of this invention, has a satisfactory solder penetrability. On the other hand, as can be seen from Figure 1, the solder penetrability of the joint of (b), ordinary galvanized steel plate, was very poor in comparison with the other two samples.

Example 7 Some 18 litre cans were produced under the can production conditions indicated below, from the above-mentioned (a) zinc plated steel plate having a high solderability, from which oxides on the surface had been removed (IA + /IZn + = 5). (b) ordinary galvanized steel plate, and (c) ordinary tinplate, by means of a commercial automatic can production line which is usually employed to produce 18 litre cans from tin plate using soldering techniques. Various performances of the cans thus produced were investigated.

Can Production Conditions (1) Blanking, bending and interlocking operations for the zinc plated steel plate were conducted in the same manner as for (c), ordinary tinplate.

(2) The interlocking seam joints of the top or bottom plate and the body plate were uniformly coated with a flux having the same composition as in Example 6 and a solvent type flux (trade name, "TF-30" manufactured by Tokyo Soldite Co., Ltd.; Composition: ZnCl2 = a major amount, NH4CI = a minor amount, surface active agent = a minor amount, and non-ionic water = the rest, this flux being diluted with ethylene glycol monobutyl ether) by means of a felt roller.

(3) Soldering was carried out in the following manner.

Top and bottom plates: bonded with wire solder (diameter = 2.0 mm, Sn 40% by weight-Pb 60% by weight) in the same manner as conventional tinplate.

Body plate: bonded by dipping in a solder bath of 1 m length (Sn 40% by weight-Pb 60% by weight) maintained at 270-2750C for about 2 seconds.

(4) Can producing speed: 27 cans/minute.

The sectional shapes of the interlocking seam joints of the sample cans thus produced are shown in Figure 2. As can be seen from this figure, (a), the zinc plated steel plate of this invention, has a satisfactory solder penetrability equivalent to that of (c), the ordinary tinplate. Thus, it was shown that the zinc plated steel plate of this invention provides no problems with regard to can production efficiency including the solderability of the interlocking seam joint. On the other hand, the solder penetrability of the interlocking seam joint of (b), ordinary galvanized steel plate, was very poor as in Example 6.

The above produced cans were also subjected to an air-tightness test and a breaking strength test. The breaking test was conducted by dropping a can filled with water. As can be seen from the results shown in Table 6, the can of this invention and the tinplate can were both satisfactory with regard to air-tightness and breaking strength. On the other hand, the air-tightness of the can produced from (b), the ordinary molten zinc plated steel plate, was very poor since the solder penetra bility of the interlocking seam joint was insufficient as shown in Figure 2.

This is a major defect, and this can is useless as an 18 litre can.

TABLE 6-Performance of 18-Litre Can

Can of this Comparative Comparative invention can can Starting (a) Molten zinc plated steel (b) ordinary galvanized (c) ordinary tinplate material plate having satisfactory steel plate solderability Appearance of satisfactory not satisfactory satisfactory soldered part (discontinuously soldered) Air-tightness (1) completely air-tight up to a impossible to pressurize completely airtight up to a (Internal pressure of 1.5 kglcm2 (not airtight) pressure of 1.5 kg/cm2 pressurizing test; Breaking no water leaked (sufficient - no water leaked (sufficient strength(7' strength) strength) Note: (1) Airtightness was tested by placing a sample can in water and pressurizing the inside of the can by a compressorto checkfor leakage of air.

121 Breaking strength was tested bydroppings sample can filled with18 litres ofwater from a height of 3 meters above the ground to check the breakage state, thereby evaluating the bonding strength ofthe interlocking seam joint.

Example 8 Some 18 litre cans were produced under the fol lowing can production conditions from the above mentioned (a), zinc plated steel plate of this inven tion having a high solderability, (b), ordinary galvan ized steel plate, and (c), ordinarytinplate, by means Df acommercial can production line which is usually employed to produce 18 litre cans from tinplate using wire solder to bond both a top or bottom plate and a body plate. Various performances of the cans thus produced were investigated.

Can Production Conditions (1) Blanking, bending and interlocking operations of the zinc plated steel plate were conducted under the same conditions as for (c), ordinary tinplate.

(2) The interlocking seam joints of the top or bottom plate and the body plate were bonded by means of the wire solder method using rosin-containing wire solder (diameter = 2.0 mm, Sn 40% by weight-Pb 60% by weight).

(3) Can producing speed: 24 cans/minute.

The above produced cans were subjected to an air-tightness test and a breaking strength test in the same manner as in Example 7. As a result of these tests, it was found that the can of this invention produced from (a), the zinc plated steel plate having a high solderability, had satisfactory air-tightness and breaking strength (i.e. soldering strength) equivalent to those of the tin can produced from (c), the ordinary tinplate. On the other hand, the can produced from (b), the ordinary galvanized steel plate, was not airtight and it was impossible to pressurize the inside of the can. Thus, it was found that it is impossible to produce an 18 litre-can from (b), the orindary molten zinc plated steel plate, using normal soldering techniques.

As mentioned above, the zinc plated steel plate of this invention has an excellent solderability, and a can produced from this zinc plated steel plate has satisfactory air-tightness and soldering strength equivalent to those of conventional tinplate cans. The zinc plated steel plate of this invention having a high solderability is cheaper and more corrosion-resistant than conventional tinplate. Various cans such as a 18 litre-can or a plain can can be produced using the same equipment under the same production conditions and soldering conditions as used in the production of conventional tinplate cans. A can produced from the zinc plated steel plate of this invention has higher corrosion-resistance, and can be produced at a lower cost than conventional tinplate cans. Thus, the development of the zinc plated steel plate can of this invention is comparable to the conventional tinplate cans leading to the saving of tin resources.

Furthermore, the zinc plated steel plate can of this invention is more satisfactory in respect of cost, productivity, and corrosion-resistance than a tin-free steel plate can produced by the use of seam welding or a special bonding agent. Thus, the zinc plated steel plate of this invention has a great commercial value.

Claims

1. A zinc plated steel plate at least one surface of which is substantially free from oxides and coated with an anti-rust film.

2. A zinc plated steel plate as claimed in Claim 1, wherein the anti-rust film is of an acryl type resin.

3. A zinc plated steel plate as claimed in Claim 2, wherein the anti-rust film has a thickness of 1.0-20 1cm.

4. A zinc plated steel plate as claimed in Claim 1, wherein the anti-rust film is of a petroleum type wax.

5. A zinc plated steel plate as claimed in Claim 4, wherein the anti-rust film has a thickness of 2.0-20 ,am.

6. A zinc plated steel plate as claimed in Claim 1, wherein the anti-rust film is of an alkyd type resin.

7. A zinc plated steel plate as claimed in Claim 6, wherein the anti-rust film has a thickness of 1.0-15 ,am.

8. A zinc plated steel plate as claimed in any of Claims 1 to 7, which is a galvanized steel plate having an etched surface.

9. A can according to Claim 7, substantially as herein described in any of the foregoing Examples.

9. A zinc plated steel plate as claimed in any of Claims 1 to 7, which is a zinc electroplated steel plate.

10. Azinc plated steel plate as claimed in any of Claims 1 to 7, which is a zinc vapour deposited steel plate.

11. A zinc plated steel plate substantially as herein described with reference to, and as shown in, Figure 1a of the accompanying drawings.

12. A zinc plated steel plate according to Claim 1 substantially as herein described in any of the foregoing Examples.

13. A can produced from zinc plated steel plate as claimed in any of Claims 1 to 12, the can having an interlocking seam joint bonded by soldering.

14. A can according to Claim 13, substantially as herein described with reference to, and as shown in, Figure 2a of the accompanying drawings.

15. A can according to Claim 13, substantially as herein described in any of the foregoing Examples.

New claims or amendments to claims filed on 3rd June 1980.

Superseded claims 1 to 15.

New or amended claims:

1. A zinc plated steel plate having improved solderability prepared by plating a steel plate with zinc from a zinc bath containing at least O.i% by weight of aluminium, removing the oxides from the surface of the thus-plated steel plate such that the surface, up to a depth of 200 Angstroms, is substantially free from oxides to such a degree that the ratio of the aluminium ion detection intensity (lAl +)/zinc ion detection intensity (lzn +) is not higher than 20 at the maximum as measured by a microanalyzer, and coating the thus-treated surface with an anti-rust film which is an acryl type resin, a petroleum type wax or an alkyd type resin to such an extent that the film has a thickness of 0.1-20 microns.

2. A zinc plated steel plate as claimed in Claim 1, wherein a said petroleum type wax anti-rust film has a thickness of 2.0-20#m.

3. A zinc plated steel plate as claimed in Claim 1, wherein a said alkyd type resin anti-rust film has a thickness of 1.0-15 ELm.

4. A zinc plated steel plate as claimed in any of Claims 1 to 3, which is a galvanized steel plate, a zinc electroplated steel plate or a zinc vapour deposited steel plate.

5. A zinc plated steel plate according to Claim 1, substantially as herein described with reference to, and as shown in, Figure la of the accompanying drawings.

6. Azinc plated steel plate according to Claim 1, substantially as herein described in any of the foregoing Examples.

7. A can produced from zinc plated steel plate as claimed in any of Claims 1 to 6, the can having an interlocking seam joint bonded by soldering.

8. A can according to Claim 7, substantially as herein described with reference to, and as shown in, Figure 2a of the accompanying drawings.