Tin Free (TFS)

Chrome-Plated Sheet Steel (T F S)

Chapter 1 Preface

The so-called Tin Free Steel(TFS) refers to "no tin but can replace tinplate use of coated steel plate". Again, TFS originally referred to any type of steel plate suitable for such use, but later specifically to thin steel plate treated with chromate electrolysis. The bottom layer of the sheet is chromium metal, and the top layer is covered with a thin film made of chromium's hydration oxide.

In order to gradually replace tinplate, the development of nickel plating, aluminum plating and other thinner plating of thin steel plate, chromium acid impregnation treatment of thin steel plate, phosphate liquid treatment of thin steel plate chemical treatment and so on. But these products from its quality characteristics, production costs, are more than by chromic acid electrolytic treatment, the bottom is chromium metal, the surface is composed of chromium hydration compounds of the thin steel plate is poor, so only the latter type of thin steel plate can replace tinplate. In order to distinguish this Type of TFS from other types of TFS in the United States, it is called TFS-CT (Tin Free Steel-Chromium Type) or TFS-CCO (Tin Free Steel-CrCr2O3 Type). But these days, whenever we talk about TFS, we mean the TFS of chromate electrolytically treated thin steel plates. Therefore, all TFS-CT or TFS-CCO presented in this paper are referred to as TFS.

TFS is considered a newly developed canning material with a relatively short history, so public information on its production methods is still scarce. It IS A PITY THAT WE CANNOT GO INTO DETAIL HERE, BUT WE WILL DO OUR BEST TO COLLECT MORE research AND survey data to meet the needs of our readers.

Chapter 2: History of TFS

As for the food can material, as mentioned in the History of tinplate, it has been valued and favored by people since the beginning of the 19th century, and with the change of dietary life, its demand has increased significantly. Even at present, it still maintains its dominant position as the mainstream can material. But it is well known that tinplate is a tin plating product on thin steel plate, and because tin production is limited to Southeast Asia, Bolivia and other countries, in the Second World War, the United States has felt the shortage of tin supply. Coupled with the political instability of these tin-producing countries themselves, tin supply will be interrupted at any time, and tin resources are increasingly exhausted.

As the demand for tin increased significantly during the Second World War, the technology for making electroplated tinplate was rapidly developed, and the traditional hot-dip tinplate with high tin content was changed to electroplated tinplate with low tin content. But this kind of tinplate with less tin plating has poor corrosion resistance.

For this reason, a manufacturing method of surface chemical treatment after electroplating was developed to enhance its corrosion resistance, as shown in Table 2-1, the anodic and cathodic treatment methods were used in aqueous solution mainly with chromate and dichromate. This thinking later led to the development of electrolytic phosphate treatment of thin steel plates.

Table 2- 1 Surface treatment of tinplate

Temperature of handling liquid

When ℃ between

(sec) current density

A/dm2 Cited literature

Drug concentration PH

Na2CrO4 · 4 h2o

Na3PO4 12 1% h2o

0.25% 11.3 21 Anodic treatment 0.6

Cathode treatment 2.4 9.3 Stevens-on-&

Schaub

K2CrO4 0.5-5% cathodic treatment of 1-10 1-2(4.5V) Prust

Na2Cr2O7 · 2 h2o

Containing phosphate 0.2-3% 2-7 26.7 Cathodic treatment followed by anodic treatment of Neish

In addition to adopting such tinplate manufacturing methods to reduce the amount of tin, we are looking forward to the emergence of a can material that does not use tin at all.

As A new can material to replace tinplate, it must be considered whether it can satisfy the following characteristics.

(1) Pay attention to no small linear rust in storage and transportation.

(2) The use of coatings and printing ink and other organic processing agents, thin steel plate surface has good infiltration, and coating, printing can not occur fisheye defects.

(3) Coating and printing after baking, punching, extrusion processing and other forming, can not cause coating peeling.

(4) Coating and printing after baking, for a variety of canning content corrosion resistance to be better.

(5) It has a high-speed canning operation comparable to the tinplate can body soldering operation.

The above are not the use of tin new can material should have the characteristics, and this new can material manufacturing method, should be as simple as possible, the design and construction of the production line should be easy; In addition, it is more economical and faster than the manufacturing engineering of tin plating can material, which are the conditions that new can material should have.

And can meet the above mentioned conditions, the first is developed by the United States of the two chemical treatment of thin steel plate method is the most eye-catching. Faced with a shortage of tin during the Korean War, American industry developed the sheet steel. Which high-profile Heintz is one of the chemical processing of steel Manufacturing and development of chromic acid hot dipping treatment ハ イ ナ ッ ク. A rival to this is the phosphate electrolytic treatment steel plate developed by U.S.Schumel.

Heintz Manufacturing, which had successfully developed the HEINAC manufacturing process, established a Pilot line with Bethlehem Steel in 1953 at the company's Sparrows Point plant to supply large quantities of test sheet steel to canning companies.

Various TESTS OF THE sheet steel PRODUCED by the above METHOD PROVED TO BE A better tank MATERIAL for liquid synthetic DETERGENT than tinplate, AND THE rapid increase in the production of liquid synthetic detergent led to the commencement of continuous production in August 1954. Furthermore, American Can is implementing the HEINAC manufacturing process at its new facility in Hamilton. Around 1955m, in order to compete with HEINAC's manufacturing method, U.S.S. teel Company developed a phosphate electrolytic treatment steel plate based on phosphoric acid and sodium dichromate aqueous solution by using thin steel plate as cathode for electrolytic treatment. This steel plate was intended to be used as canning material for liquid synthetic detergent, but its corrosion resistance and other aspects are worse than those of the HEINAC manufacturing method, so its development in this field cannot be as fast as that of the HEINAC manufacturing method.

Throughout the development of phosphate electrolytically treated steel plates, even to improve the shortcomings of the U.S.S. teel manufacturing method, the use of changes in the type of subsidy additives, and a slight increase in PH, etc., were tested. However, the results do not improve the utility of its use. We arranged this phosphate electrolytic treatment as shown in Table 2-2.

Table 2-2 Electrolytic phosphate treatment method

The polarity and time (S) temperature of the treatment solution treated by the metal

℃ current density

A/dm2 Cited literature

Drug concentration PH value

Na2Cr2O7 · 2 h2o

PO4-3

nitrate

Or potassium permanganate 1 ~ 6%

1 ~ 8.4%

1 ~ 4%

0.1 ~ 0.4% 1 ~ 2 iron

The cathode

The anode

0.25 ~ 2 49 ~

60 1.6 ~ 9.7 NEISH

CrO3

PO4-3

Zn.Mg.Ca.Mn phosphate 5 ~ 50g/L

50 ~ 100g/L iron and zinc cathode

< 0.25 10 ~

80 1.1 ~ 3.2 Ikeda Yizaki

CrO4-2, Cr2O7-2

PO4-3

PO4-3/CrO4-2

Or Cr2O7-2

Non-ionic interface active agent 0.03 ~ 0.3

0.1 ~ 0.5 g/L

2:1 ~ 4:1

0.05 ~ 0.5% 2.0 ~ 5 iron cathode

2 ~ 3 50 4 Matsuda fresh ze

CrO4-2,Cr2O7-2

PO4-3

Nitrate, permanganate, etc., non-ionic interface active agent 0.03 ~ 0.3

0.1 ~ 0.3 g/L

0.1 ~ 3% and 1.0 ~ 5 iron are interactively processed by adding AC at the cathode

5 ~ 30 40 ~

70 DC 3 ~ 7

Ac 0.1-100C /S

0.5 ~ 8

Matsuda bright ze

In addition, since 1956, Bethlehem Steel and Republic Steel in the United States had developed a manufacturing method that could compete with HEINAC manufacturing method and phosphate electrolytic treatment method. Their surface treatment was cathodic reduction method of chromic acid aqueous solution. Thus a surface treatment method was developed to form a layer of cathode skin film on the thin steel plate. This is the origin of chromate electrolytic treatment of thin steel plate. However, the initial chromic acid electrolytic treatment, the resulting skin film is just a kind of inhomogeneous chromium hydration oxide, yellow film and brown film in the majority. This film will be rough powder granular, so can not be used.

In addition, Japan has been devoted to the research of electrolytic treatment of chromate since 1955, and published various methods as shown in Table 2-3 and Table 2-4 from 1959 to 1973. First, the Hi-Top industrial production of Toyo steel plate in 1961 opened the prelude to the mass production of today's TFS. Hi-Top manufacturing method has the tendency to replace tinplate, first was widely used in art cans, mixed cans and other household goods can industry. In 1962, Fujifilm Steel began producing Cansuper, a chrome-plated steel plate. At that time, Hachata iron production was based on the generation of chromium hydrate oxide on the steel plate to improve its corrosion resistance. At that time, a large number of papers on chromate electrolytic treatment were published and practical tests were carried out. However, in these methods, especially in the case of transparent raka, the product has interference color, so the color is dark. The corrosion resistance becomes worse after heating. Therefore, in addition to further research and improvement of this method, a primary electrolytic treatment method, such as Hi-top manufacturing method, has been developed. This new method is to form a skin film composed of chromium metal and chromium hydration oxide on the steel plate. In 1966 we called the products produced by this method Supercoat and started production. After that, Hachiman and Tomato Iron merged into New Japan Iron, and with the birth of this new Japan Iron, from July 1971, the two iron mills began to produce TFS, collectively known as Cansuper. Then in 1972, Japanese steel pipe began the real production of TFS, and named Britecote officially launched. The current Hi-Top, Cansuper and Britecote have their own characteristics in their manufacturing methods, and the surface coating formed, no matter which is the TFS formed by the extremely thin metal chromium layer and the hydration oxide layer of chromium.

Table 2-3 Chromic acid electrolytic treatment of hydrated oxides forming chromium

The polarity and time (S) temperature of the treatment solution treated by the treated metal

(° C) current density

A/dm2 references

The literature

Drug product concentration degrees

CrO3

H3BO3, Na2O7

10H2O

Cr+3(full chrome) 100 ~ 400g/L

8 g/L ~ saturated

2 ~ 18% Fe and Zn cathode

> 10 20 to 45 5.4 to 32 Wick

CrO3

H3BO3, Na2O7

10 h2o 100 ~ 400 g/L

8g/L ~ saturated Fe, Zn,

Sn, cathode > 21 5.4 ~ 32 Wick

Schneide-wind

CrO3

H3PO4

CrO3 / H3PO4 10 ~ 35%

3 ~ 12%

2 ~ 3% Fe, Cu,

Ni, Sn, anode

The cathode

1 to 20 36 to 66 8.1 to 54 Loveland

Prust

CrO4-2 Cr2O7-2

Cr+3 (reduced with tartaric acid, nitric acid, etc.) 0.1 ~ 15%

0.1 ~ 10% Fe cathode

> 0.25 20 ~ 80 1.1 ~ 3.2 Toshima

M battery

kamata

CrO3

Cr+3

H3PO4

H3BO3 10 ~ 20 g/L

1 ~ 5 g/L

3 ~ 10 g/L

1 ~ 20g/L Fe cathode

> 0.25 15 ~ 18 1.1 ~ 3.2 meters

kamata

Na2Cr2O7 H3PO4

(NH4)2SO4

CO(NH2)2

Any of Cr2(SO4)3 200g/L Fe, Zn,

Sn cathode 10 ~ 60* 30 ~ 50* 40* Sekawa

sakai

Cr+6

Cl- or F-5 ~ 50g/L

10 ~ 200 mg/L

PH<1.3 Fe cathode 1 ~ 3(example) 10 ~ 80 11.6 ~ 32

(Example) Yousaki

kamata

sakai

pool

Cr+6

Halooxic acid ion 1 ~ 200g/L

Fe, Zn, PH<1.5

Al cathode 0.1 ~ 1 10 ~ 90 6 ~ 20

(Example) Yousaki

kamata

Temple mountain

And nearly

CrO3

K3AlF6 10 ~ 300 g/L

0.5 ~ 2 g/L

Fe cathode

5

(Example) 20 ~ 60 5 ~ 100 Okada

tamura

CrO3 100 ~ 150g/L Fe cathode 1 ~ 5 45 ~ 60 22~86 GURRY

CrO3

Acid containing Ti, W, Mo, Se, Zn, V, As 10 ~ 100g/L

0.1 ~ 5 g/L

Tellurium acid

10 ~ 100g/L Fe cathode

<5 20 ~ 60 10 ~ 50 Wells

Mr Okada

CrO3 (Example)

Fluorosilicate 50g/L

2 g/L Fe cathode

2 40 5 Uchida

LiuFu

Table 2-4 Chromic acid electrolytic treatment of hydrated oxides formed from chromium metal and chromium

The polar temperature of the treated liquid treated by the treated metal

℃ current density

(A/dm2) time

(sec) References

The drug concentration

CrO3

Aromatic disulfide acid 20 ~ 100g/l

0.2-4.0g/l Fe, Al cathode 40 ~

70 1 ~ 30 North Village

CrO3

Cr+3

H2SO4

A compound of fluorine

Cr + 6 / Cr + 3 40 ~ 100 g/l

0.2 2.5 g/l

0.1 0.3 g/l

< 1.0 g/l

20 ~ 150 Fe, Al cathode 40 ~

70 12.5< appropriate pericytes

kitamura

dry

CrO3

Cr2 (SO4) 3 or

- H2SO4 10 to 50 g/l

0.2 ~ 5%

(the needle