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Home Material Sciences Low-toxicity production of solderable tin-free steel

Low-toxicity production of solderable tin-free steel

Description

The production of tin-free steel instead of the tinplate (for packing of dry and granular foodstuffs) has been ceased due to the necessity of using of hexavalent chromium compounds. According to the proposed production process, a thin (0.07, 0.14 or 0.21 g/sq.m/side) protective lustrous amorphous composite chromium coating is obtained using an electrolyte based on trivalent chromium compounds. Then the chromium-plated steel sheet is passivated in a chromium-free low-toxicity electrolyte and soldered with tin solder during the manufacturing of cans.

The basic production items are:

  • The developed chromium-plating technology based on a sulfate-acetate compound of trivalent chromium.
  • The developed chromium-plating technology based on a sulfate-formiate compound of trivalent chromium.

These technologies are alternative, interchangeable and provides formation of amorphous coatings on canned food steel sheet. Forming of an amorphous structure in chromium coating leads to an increase of its protective ability while maintaining the adhesive strength, mechanical durability and plasticity characteristics. This ensures an adequate corrosion resistance of the passivated chromium-plated (0.07-0.21 g/sq.m/side) steel sheet in various foodstuff media.

  • The developed passivating technology that provides forming of a colorless protective film on the chromium-plated steel sheet during 2-3 s.
  • The developed technology for soldering of tin-free steel using tin solder. The basis of this technology is the developed flux whose usage for soldering tin-free steel enables to upgrade the solder spread coefficient to 2.5-3.0 (the standard norm being not less than 1.0).

Innovative Aspect and Main Advantages

The proposed tin-free steel production process is based on four potential inventions that are grounded on the usage of the recently found phenomenon of the structure formation in the metallic materials being electrochemically deposited through a stage of liquid state (see O.B. Girin. Phase Transformations in the Metallic Materials being Electrodeposited and Their Application for the Development of Advanced Technologies for Anticorrosive Protection of Canned-Food Steel Sheet // Materials Science Forum (Switzerland). – 2007. – V.561-565. – P.2369-2372).

The major advantages of the production technology:

  • Elimination of hexavalent chromium compounds during the electrochemical deposition of the chromium coating onto the steel sheet and its subsequent cathode passivation.
  • The reduction of the chromium coating weight to 0.07-0.21 g/sq.m/side while preserving its protective and decorative properties, with the resulting reduction of the chromium and electric energy consumption.
  • Soldering of tin-free steel becomes commercially feasible.
  • Increased rate of chromium deposition onto the steel sheet to 0.01-0.015 μm/s.
  • The adequate corrosion resistance of the passivated chromium-plated steel sheet in various foodstuff media.
  • Increased protective ability of the passive film by two times in comparison to the protective ability of the passive films obtained in commercially used electrolytes containing chromium compounds.
  • Application of a simplified system for water effluents cleaning.
  • The production process does not require any capital expenditure and is applicable to existing equipment.
  • The developed additives to the flux, chromium-plating and passivating electrolytes are low toxic and not expensive. Their synthesis can be performed at any chemical facility.

Areas of Application

  • Metallurgical industry: production of tin-free steel.
  • Canned food industry: manufacturing of food cans.
  • Light industry: manufacturing of packing tare.

Stage of Development

Prototype is available for demonstration and testing, patent and marketing searches have been carried out, secret know-how is present, documents are being prepared for patenting of the inventions.

Contact Details

Ukrainian State University of Chemical Engineering
Contact person: Prof. Oleg Girin
Address: 8, Prospekt Gagarina, Dnipropetrovsk 49005, Ukraine
Теl: (380562) 337136 / 682166 / 679725
Fax: (380562) 337136 / 679725 / 473316
E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

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