Platinum coated titanium

Cathodic Protection Systems. Metal anodes using either platinum [7440-06 ] metal or precious metal oxide coatings on titanium, niobium [7440-03-17, or tantalum [7440-25-7] substrates are extensively used for impressed current cathodic protection systems. A prime appHcation is the use of platinum-coated titanium anodes for protection of the hulls of marine vessels. The controUed feature of these systems has created an attractive alternative... 

By a mechanism similar to that discussed in relation to platinum coating, titanium can function as a conducting jig to support aluminium components and assemblies in conventional anodising baths. In this application the exposed titanium acquires the insulating film, but allows current to pass to the aluminium at the points of contact . 

Platinum Platinum-coated titanium is the most important anode material for impressed-current cathodic protection in seawater. In electrolysis cells, platinum is attacked if the current waveform varies, if oxygen and chlorine are evolved simultaneously, or if some organic substances are present Nevertheless, platinised titanium is employed in tinplate production in Japan s. Although ruthenium dioxide is the most usual coating for dimensionally stable anodes, platinum/iridium, also deposited by thermal decomposition of a metallo-organic paint, is used in sodium chlorate manufacture. Platinum/ruthenium, applied by an immersion process, is recommended for the cathodes of membrane electrolysis cells. ... 

Pb02 is also applicable as a coating on a suitable carrier material (see Sect. 2.4.1.1.10). Pb02-coated titanium anodes with good stability are commercially available. On platinum or platinum-coated titanium a coating of Pb02 for laboratory use can easily be prepared electrochemi-cally (e.g. [28]). 

Smooth platinum, lead dioxide and graphite are anode materials commonly used in electrooxidation processes. All show large overpotentials for oxygen evolution in aqueous solution. Platinum coated titanium is available as an alternative to sheet platinum metal. Stable surfaces of lead dioxide are prepared by electrolytic oxidation of sheet lead in dilute sulphuric acid and can be used in the presence of sulphuric acid as electrolyte. Lead dioxide may also be electroplated onto titanium anodes from lead(Il) nitrate solution to form a non-porous layer which can then be used in other electrolyte solutions [21],... 

For the CI2/CI system a platinum-coated titanium electrode becomes passive when the anodic overvoltage is more than about 0.2 V, presumably because the rate-determining step cr — e Cl(adsorbed) no longer takes place easily on the electrode surface. 

Hiller K, Rothschild JM, Fudge W et al. A randomized comparison of a bipolar steroid-eluting lead and a bipolar porons platinum coated titanium lead (Abstract). PACE 1991 14 695. 

Platinised titanium anodes (titanium carrying a thin surface film of platinum, of the order of 0-0025 mm thick) have proved successful in cathodic-protection systems employing impressed-current techniques, as electrodes for electrodialysis of brackish water, and in many applications where established anode materials suffer significant corrosion. Platinum-coated titanium anodes can operate without breakdown at very high current densities, of the order of 5 0(X)A/m, in sea water, as although the very thin platinum coating may be porous the underlying titanium exposed at the pores will become anodically passivated... 

The greatest immediate use for platinum-coated titanium is for anodes in the chlorine-caustic industry. Some horizontal-type chlorine cells use e anded metal anodes. From 1.3 to 2.5 pm (0.05 to 0.1 mil) of platinum is appHed to the anode surface. Replating of the anodes may be required afler about 2 years, depending on the operating conditions. The attrition rate for platinum appears to be about 0.6 g/tonne (0.5 g/ton) of dilorine. 

When the conductivity of the medium is weak, which is the case in fresh water, cathodic protection is provided by nonsacrificial anodes, made for example in platinum-coated titanium, which operate with an external direct current source. 

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