In vitro corrosion behavior of cast iron-platinum magnetic alloys.
OBJECTIVE
The objective of this study was to investigate the corrosion resistance of cast Fe-Pt alloys of varying compositions for use as attachment keepers and to make a comparison with the corrosion resistance of magnetic stainless steel.


METHODS
The corrosion behavior of cast Fe-Pt alloy keepers (Fe-40 at%Pt, Fe-38 at%Pt, Fe-37 at%Pt and Fe-36 at%Pt) was evaluated by means of an immersion test and an anodic polarization test. The solutions used were a 1.0% lactic acid aqueous solution (pH=2.3) (10 ml) and 0.9% NaCl solution (pH=7.3) (10 ml). As a control, the corrosion resistance of a magnetic stainless steel keeper (SUS 447J1: HICOREX) was also measured.


RESULTS
Chromium and platinum ions were not detected in either the 1.0% lactic acid or 0.9% NaCl solutions. The only released ions detected were the Fe ions in the 1.0% lactic acid solution. The amounts of Fe ions released from the Fe-40 at%Pt and Fe-38 at%Pt alloys were significantly (p<0.05) lower than from the Fe-37at%Pt, Fe-36 at%Pt and SUS 447J1 alloys. In the anodic polarization test, the potentials at the beginning of passivation for the four Fe-Pt alloys were higher than for the SUS 447J1 alloy in both solutions.


CONCLUSIONS
The Fe-Pt alloys, especially the alloys with higher Pt percentages (Fe-40 and 38 at%Pt), indicated a high corrosion resistance compared to the magnetic stainless steel keeper. A reduction in the Pt percentage may decrease the corrosion resistance in the oral environment.
Department of Fixed Prosthodontics, Nagasaki University, School of Dentistry, Nagasaki, Japan.
I
I
Watanabe
K
K
Hai
Y
Y
Tanaka
K
K
Hisatsune
M
M
Atsuta
D002857:Chromium / Q000737:chemistry; D003343:Corrosion; D003722:Dental Alloys / Q000737:chemistry*; D003734:Dental Casting Investment / Q000737:chemistry; D004563:Electrochemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007101:Immersion; D007501:Iron / Q000737:chemistry*; D019344:Lactic Acid / Q000737:chemistry; D008280:Magnetics / Q000295:instrumentation*; D008422:Materials Testing; D010984:Platinum / Q000737:chemistry*; D015203:Reproducibility of Results; D012965:Sodium Chloride / Q000737:chemistry; D013193:Stainless Steel / Q000737:chemistry; D013499:Surface Properties
D003722:Dental Alloys; D003734:Dental Casting Investment; D002857:Chromium; D013193:Stainless Steel; D019344:Lactic Acid; D012965:Sodium Chloride; D010984:Platinum; D007501:Iron