Glass-fused-to-steel tanks

Since 1994, APRO Industrie has been supplying and installing glass-dused-to-steel steel tanks up to 25,000 m3 capacity.
APRO Industrie enamelled steels – which meet quality standard ISO EN 28765:2011 – provide the best possible combination of the strength and flexibility of steel and the inertness of glass. According to the range and the vitrification qualities, enamelled steel is as suitable for the most severe applications as for more economical storage solutions.

Elaboration of our enamelled steels

Enamelled steel, also known as glass-lined steel or glass-fused-to-steel, is the result of coating the steel with glass in fusion at high temperature (850°C).

The enamelling of steel for the construction of tanks, is a process requiring considerable know-how and involving many inspection stages in order to guarantee “zero defect” quality reliably and continuously.
The diagram below shows the various manufacturing stages of our enamelled steels:


1. Receipt of the raw steel
2. Drilling and cutting out of the sheet
3. Shot blasting of the sheet
4. Forming
5. Chemical cleaning
6. Pre-protective passivation
7. Application of a nickel-rich coating
8. Drying
9. Application of a cobalt-rich coat of liquid enamel
10. Pre-stoving
11. Fusion in ovens at 850°C
For double enamelling:
12. Application of a second coat of enamel
13. Pre-stoving
14. Fusion in ovens at 850°C
Then for all the enamelled sheets:
15. High voltage test (700 V, 1100 V or 1500 V according to the enamel quality required).
16. Packaging
The coating of the steel sheets used on our tanks is performed exclusively in our ISO 9001 certified factories, in accordance with rigorous and carefully controlled processes.
Throughout the process, sampling tests (see the “standards” paragraph below) and thickness measurements are performed. All these stages are undertaken in controlled atmosphere conditions: hygrometry, dust, temperature etc.
Prior to leaving the factory, all the parts are tested electrically at 700 V, 1100V or 1500V. An electric arc is generated if the test probe encounters a discontinuity or an irregularity in the coating. Any parts containing discontinuities are systematically rejected, thus guaranteeing a “zero defect” product.
The composition of our enamel, the quality of its elaboration, and the quality tests which our products are subjected to, provide our tanks with an unequalled anti-corrosion protection. Coatings applied in situ, in particular, have a significantly diminished service life and durability compared with our coatings applied in the factory under strict controlled atmosphere conditions.
APRO Industrie offers five ranges of enamelled steel tanks (from one to three coats of enamel, with single or double enamelling) to suit the characteristics of the liquids to be stored and the environmental storage conditions.
Sealing of the enamelled steel tanks is achieved using a mastic sealant whose composition is adapted to suit the storage problem concerned.

Standards and Quality

The material, the design and the manufacture of our enamelled steel tanks satisfy the requirements of standard ISO EN 28765:2011 – which covers the design of bolted enamelled steel tanks for the storage and treatment of water, urban and industrial effluents and slurries.
These tests include in particular exposure:

  • To citric acid at ambient temperature and boiling
  • To demineralised water in the liquid and water phase
  • To sodium hydroxide
  • To sulphuric acid at ambient temperature
  • To hydrochloric acid at ambient temperature and boiling
  • To most conventional detergents

As well as undergoing many mechanical tests, such as:

  • Impact test
  • Adhesion test
  • Abrasion test
  • Thermal shock resistance test
  • Scratch resistance test

Main fields of application

A few enamelled steel achievements

  • Graincourt les Havrincourt, 4,000 m3 digester, 2,000 m3 post dig, 1,200 m3 hydrolysis tank
  • Kenitra, Morocco, 1,200 m3 digester, paper industry
  • Le Creusot, Veolia, 800 m3 buffer tank
  • Donnery, Proserpol, 3,000 m3 buffer tank
  • Saint Aubin les Elbeuf, Sanofi, 1,600 m3 Biozan storage tank

Advantages of enamelled steel tanks

  • Proven technology, over 40 years experience
  • Perfectly suited to highly corrosive media (pH, temperature, chlorides, H2S up to 6,000 ppm, etc.)
  • Suitable for storing liquids which are incompatible with concrete
  • “Zero defect” quality
  • Maintenance free
  • Very great longevity (>30 years)
  • Attractive price relative to concrete, welded steel and moulded plastic from 50 m3 capacity
  • Service life of enamelled steel structures: 30 to 50 years
  • Enamel is resistant to the most corrosive effluents
  • Available in various colours to better blend in with the environment