Applications

There are many applications for continuously electrodeposited steel strip (Table 3). Most of these fall within four of the largest markets in today's economy: food containers and other general packaging, automobiles, appliances, and furniture. The first two markets account for most of the total volume of production.

Table 3 Typical applications for continuous electrodeposited coatings for steel strip

Coating

Applications

Zinc

Auto body outer panels and some structural components

Zn-Ni (10-14 wt% Ni) alloy

Auto body outer and inner panels and some structural components

Zn-Fe (10-20 wt% Fe) alloy with or without a flash of Zn-Fe (>80% Fe)

Auto body outer panels and some inner panels

Zn-Ni with thin, weldable organic coating

Auto body outer and inner panels

Zn or Zn-Ni with various post-treatments (chromate, phosphate, organic)

Doors, housings, appliances

Tin (matte)

Two-piece drawn and ironed cans, automotive oil and air filters, baking trays

Tin (reflowed)

Three-piece welded cans with and without enameling, battery cases, lighting fixtures,

Packaging and containers include the main sector, food and beverage cans (Fig. 1), as well as general-purpose containers ranging from photographic film canisters to paint and solvent cans. The steel for these containers is electrodeposited with either tin or chromium, depending on the end use and the surface lubricity requirements of the manufacturing process (Ref 2, 3, 4, 5).

Fig. 1 Examples of containers made from continuous electrodeposited strip steel

Electrolytic tin-plated strip, commonly called tinplate, is used for applications requiring severe forming, with the tin coating serving as a lubricant. The tin coating also protects steel against corrosion and protects certain foods from discoloration. It can also prevent food oxidation, because tin is a strong reducing agent in certain environments (Ref 6).

Electrolytic chromium-coated steel, more commonly called tin-free steel, was developed in the late 1960s as a lower-cost alternative to tinplate. The extremely thin coating, composed of layers of metallic and nonmetallic chromium, is both a barrier coating against corrosion and an adherence enhancer for subsequent lacquering. However, it supplies no lubricity in forming operations or for food preservation. It is used mainly for draw-redraw containers and can ends, both of which are usually manufactured after a lacquer coating is applied.

Automobiles. Continuously electrodeposited steel strip is used in the manufacturing of automobiles (Ref 7, 8, 9, 10), almost exclusively for body panels but also for components such as oil filter shells and fuel tanks. Body panels are primarily made from zinc-plated strip, referred to as electrogalvanized sheet, but also from steel sheet plated with zinc alloys (Zn-Ni or Zn-Fe).

From 1986 to 1991, in the United States as well as throughout Europe and Asia, there was a tremendous increase in electroplating capacity and in the production of electrogalvanized sheet (Tables 4, 5, 6). This occurred because of the need to make outer body panels more resistant to corrosion in hot, humid, and marine environments and in regions where there is frequent use of deicing salt. Electrogalvanized steel was selected by most automakers for its superior surface quality vis-à-vis that of the hot-dipped galvanized products available at the time. The zinc coating generally follows the texture of steel and has no significant effect on surface roughness or paint appearance. Zinc was also chosen because of its galvanic or sacrificial protection of steel in areas where paint, which simply provides barrier protection for the steel, is scratched or otherwise damaged.

Table 4 Major U.S. electrogalvanizing lines and their capabilities

Plating line location

Nominal capacity(a), tons/y

Plating cells

Total amperage kA

Coatings

Start-up

No.

Type

Middletown, OH

250,000

16

Gravitel

736

Zn

1986

280,000

21

Gravitel

1,056

Zn, Zn-Ni

1991

Dearborn, MI

700,000

42

CAROSEL

2,352

Zn, Zn-Fe

1986

Cleveland, OH

400,000

20

Vertical

1,320

Zn

1986

Columbus, OH

300,000

15

Vertical

990

Zn, Zn-Ni, Zn-Ni + organic

1991

Ecorse, MI

400,000

20

Vertical

1,000

Zn

1985

Gary, IN

400,000

18

CAROSEL

900

Zn

1977

Walbridge, OH

400,000

20

Gravitel

1,000

Zn, Zn-Ni, Zn-Ni + organic

1986

New Carlisle, IN

400,000

24

Gravitel

1,200

Zn, Zn-Ni

1991

Total

3,530,000

Source: Updated from Ref 7

(a) Nominal capacity figures represent rough estimates made by the author from miscellaneous data.

Table 5 Major European electrogalvanizing lines started since 1980

Plating line location

Nominal capacity, tons/yr

Plating cells

Total amperage, kA

Coatings

Width

Start-up

No.

Type

mm

in.

Linz, Austria

200,000

12

Gravitel

360

Zn, Zn-Ni

1600

63

1985

Ste. Agathe, France

300,000

16

CAROSEL

928

Zn, Zn-Ni

1830

72

1983

Beautor, France

220,000

8

Radial

400

Zn, Zn-Ni

1520

60

1976

Mardyck, France

200,000

12

CAROSEL

600

Zn

1900

75

1991

Dormund, Germany

150,000

5

Vertical

300

Zn

1950

77

19S6

Bochum, Germany

150,000

10

Horizontal

360

Zn

1600

63

19S7

Neuwied, Germany

150,000

15

Vertical

320

Zn-Ni

1570

62

19S5

Salzgitter, Germany

300,000

13

Gravitel

650

Zn

1S50

73

19S7

Duisburg, Germany

200,000

11

Horizontal

450

Zn

1900

75

19S7

Torino, Italy

200,000

16

Radial

512

Zn

1600

63

19S7

Genoa, Italy

S0,000

10

Radial

320

Zn

1S50

73

1991

Potenza, Italy

30,000

6

Horizontal

60

Zn

1S00

71

19SS

Varzi, Italy

50,000

4

Radial

100

Zn

1400

55

19S6

Luxemburg

60,000

S

Vertical

150

Zn

1550

61

19S3

Sagundo, Spain

60,000

4

Horizontal

160

Zn

1700

67

19S6

Shotton Works, Deside, Wales

200,000

S

Vertical

52S

Zn, Zn-Ni

1600

63

1972/19S9

Genk, Belgium

300,000

10

Vertical

600

Zn, Zn-Ni

10S0

43

Table 6 Major Asian electrogalvanizing lines started since 1976

Plating line location

Nominal capacity, tons/yr

Plating cells

Total amperage, kA

Coatings

Width

Start-up

No.

Type

mm

in.

Mizushima, Japan

360,000

19

Radial

662

Zn, Zn alloy

1S30

72

19S7

300,000

Horizontal

Zn, Zn-Ni

1S30

72

1991

Chiba, Japan

300,000

7

Radial

310

Zn, Zn-Ni

1700

67

19S2

Fukuyama, Japan

360,000

11

Horizontal

550

Zn, Zn-Fe

1SS0

74

19S3

300,000

12

Horizontal

500

Zn, Zn-Ni

1830

72

1987

240,000

7

Horizontal

350

Zn

1830

72

1992

Nagoya, Japan

360,000

17

Horizontal

640

Zn, Zn-Fe

1830

72

1983

Kimitsu, Japan

300,000

6

Horizontal

320

Zn, Zn-Ni, Zn-Ni + organic

2080

82

1985

Kashima, Japan

360,000

14

Vertical

672

Zn, Zn-Ni

1600

63

1984

180,000

8

Vertical

384

Zn, Zn-Ni, Zn-Ni + organic

1600

63

1988

Wakayama, Japan

260,000

10

Horizontal

196

Zn, Zn alloy

1880

74

1968/1986

Kakogawa, Japan

360,000

10

Horizontal

400

Zn, Zn alloy

1600

63

1986

300,000

Horizontal

Zn, Zn-Ni

1830

72

1991

Sakai, Japan

200,000

12

Horizontal

Zn-Ni

1600

63

1986

Hanshin, Japan

140,000

3

Horizontal

120

Zn, Zn alloy

1830

72

1986

Kwangyang, Korea

400,000

20

Radial

1008

Zn, Zn-Fe

1860

73

1990

Pohang, Korea

300,000

12

Radial

448

Zn, Zn-Ni

1650

64

1986

Kaohsiang, Taiwan

200,000

6

Radial

336

Zn, Zn-Ni

1676

66

Source: Ref 10

Furniture and appliances markets make use of zinc and zinc alloy continuously plated steel strip. Metal office furniture, for example, may be manufactured using electrogalvanized sheet, normally with only a "flash" (about 1 to 2 pm) of zinc coating. Appliances such as toasters, dishwashers, washing machines, dryers, and so on may also be manufactured in part from further treated and painted electrogalvanized steel for extra corrosion protection.

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