PdCl2 Solution Research Articles

Corrosion resistance of porous titanium in some aggressive media

1. Titanium specimens, of 30% porosity, prepared from an electrolytic powder of the −1 +0.25 mm fraction exhibit low corrosion resistance in 40%H2SO4 and 20%HCl solutions at room temperature. Specimens nitrided at 850°C for 30 min differ only little in this respect from specimens which have not been nitrided. 2. The nitriding of such specimens for 8 h at 850°C substantially increases their resistance to corrosion by 20% HCl. After 600 h of testing, the electrical resistivity of the specimens rises only negligibly and their surface remains bright. The corrosion resistance of such specimens in 40% H2SO4 is essentially no different from that of specimens from pure titanium. 3. The surface alloying of titanium powder with 2, 0.2, and 0.1% palladium, performed from a PdCl2 solution, passivates specimens prepared from such powder in 20% HCl, as a result of which they resist corrosion in this acid at room temperature and holding periods of up to 600 h. Specimens containing 0.05% palladium begin to corrode after 400 h of holding in this acid. In 40% H2SO4, passivity of specimens is attained by introducing 2 or 0.2 wt.% palladium into titanium powder. Decreasing the palladium addition to 0.1 or or 0.05 wt.% lowers the corrosion resistance of titanium specimens. 4. Specimens of all the porous titanium materials investigated are totally immune to corrosion in 30% caustic soda solutions.

Colorimetric determination of iron (III) with 1,10-phenanthroline

A new procedure has been developed for the colorimetric determination of iron(III). It consists in the reduction of iron (III) in dilute sulphuric acid medium (0.1 to 1.0 N) with an excess of hypophosphite (1∶100) at room temperature using one or two drops of 0.1% PdCl2 solution as catalyst, and then complexing the reduced iron with 1.10-phenanthroline. Iron (III) can also be reduced with phosphite using the PdCl2 catalyst and boiling for 5 to 10 min on a hot plate. The molar concentration of phosphite is preferably kept 500 times that of ferric ion.