DSA® anodes for chlorine evolution

From the chlor-alkali industry to water disinfection and water treatments, De Nora DSA® anodes are the invisible building blocks in thousands of products that make life healthier and more comfortable.


Insoluble oxide coated electrodes are an invention of Belgian scientist Henri B. Beer. During his research work, he noted that:

  • Titanium is very stable in Cl2-containing brine
  • Platinum group metals are robust against anodic polarization, especially in form of oxides
  • Ruthenium in the cheapest among platinum group metals

He was the first in proposing the unique idea of directly bonding an oxide layer on the surface of a base metal without any intermediate layer.

The oxide-coated metal anode was first patented in 1965.

The company for which Dr. Beer was carrying out his reaserch was not interested in this invention and his patents were bought by Oronzio de Nora who further developed the concept, testing new combination of elements for producing mixed metal oxide coatings with different characteristics and performances.

The first industrial application of De Nora DSA® anodes was in the chlor-alkali electrolysis, starting with mercury process. The replacement of graphite consumable anodes with De Nora DSA® anodes resulted in a reduction of the power consumption for electrolytic caustic soda production from 3800 to <3200 kWh/ton-NaOH.


When graphite consumable anodes were substituted with De Nora DSA® anodes, the power consumption for electrolytic caustic soda production decreased from 3800kWh/ton-NaOH to <2000 kWh/ton-NaOH, almost the half.

This incredible result allowed design of more compact cells, less maintenance work and a tremendous boost in productivity. Introduction of De Nora DSA® anodes revolutioned not only the electrode industry but the electrolysis process.  If no DSA, IM process could not be completed.

Soon De Nora DSA® anodes where applied to diaphragm process and then to IM process, with the greatest improvement of both anode and cathode structure to zero gap technology.