We are specialised in creating world class mixed metal oxide (MMO) coated titanium anodes for various industry applications.
All electrodes are made from two core components: a base and a coating.
The coating is similar to a varnish, although quite different in composition and application method and its purpose is to allow the electrochemical reactions. It needs a support which supplies it with the necessary mechanical structure which constitutes the electrode.
Among the many materials tested, we have chosen Titanium as it has the physical and chemical characteristics required to host the coating, is able to resist to the chemically aggressive environments of the processes it is used in while being ideal for the current’s conduction.
Additionally, Titanium can be manufactured and worked to a wide range of shapes: sheets, nets, tubes, wires, complex manufactured products etc.
The final electrode is the result from the combination of the coating and the Titanium, taking different commercial names such as MMO etc…
Under a durability perspective, while the coating wears out slowly, the main benefit Titanium is that it remains unaltered in time. An electrode which has lost all or part of its coating during its life can be regenerated with subsequent coating applications a virtually unlimited number of times.
An electrode can be used, depending on the process it’s designed to be used in, either as a cathode or an anode.
Used as a cathode, for example in the membrane Chlorine–Alkali process, the electrode base is made of Nickel, while the coating maintains its noble metals-based composition.
The coating is very thin layer, typically just a few microns, made of noble metal oxides part of the Platinum family, that covers the titanium’s surface where the anodic reaction takes place.
We use primarily Ruthenium and Iridium, mixed, depending on the application, with other metals from the same family: Palladium, Rhodium, Platinum.
Titanium family’s oxides are part of the coating’s formula as well: Titanium, Tantalum, Niobium. They serve the purpose to make the structure more compact and adherent to the Titanium base and at the same time provide a protective function against the aggressiveness of some solutions the electrodes need to work in.
The formation of the coating takes place through the application of a solution of the above elements and a subsequent high temperature thermal treatment to create the oxide.
Each application or “coat” is a cycle during which a fraction of the coating’s quantity settles. The number of cycles is subject to the final noble metal’s load, which, in turn, is in relation to the type of application it is designed for.
There are many formulations or “recipes” for coatings, each one specifically engineered for its final use as well as for the family they belong to: anode or cathode coatings.
Among the anode coatings: coatings for Chlorine evolution, coatings for Oxygen evolution or mixed coatings.
The key component (catalyst) of the coating for Chlorine evolution is Ruthenium Oxide while for Oxygen evolution Iridium Oxide is the industry standard.
Membrane cell cathode coatings are based on Ruthenium Oxide or Platinum, mixed with Palladium and Rhodium.
A coating for each process
There are two main anodic reaction families and they are:
- The production of Chlorine (Cl2) from solutions containing Chlorides (Cl-) according to the electrochemical reaction:
Cl- + e- —-> Cl2
- The production of Oxygen (O2) from acid solutions containing mainly Nitrates, Sulphates according to the electrochemical reaction:
2H2O —-> O2 + 2e- + 2H+