Corrosion of three experimental AgMn-based casting alloys

Kawashima, Isao; Berzins, David W; Sarkar, Nikhil K; Ohno, Hiroki

« Previous Next »Dental Materials
Volume 14, Issue 6 , Pages 448-452, November 1998

Corrosion of three experimental AgMn-based casting alloys

Isao Kawashima
- Department of Dental Materials Science, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido, JAPAN
- Address correspondence and reprint requests to: Isao Kawashima, Department of Dental Materials Science, School of Dentistry, Health Sciences University of Hokkaido, 1757 Kanazawa, Ishikari-Tobetsu, Hokkaido, 061-02 Japan. Phone: +81-1332-3-1386; Fax: +81-1332-3-1386
David W Berzins
- Department of Operative Dentistry and Biomaterials, School of Dentistry, Louisiana State University, New Orleans, Louisiana, USA
Nikhil K Sarkar
- Department of Operative Dentistry and Biomaterials, School of Dentistry, Louisiana State University, New Orleans, Louisiana, USA
Hiroki Ohno
- Department of Dental Materials Science, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido, JAPAN

Received 26 August 1998; accepted 2 November 1998.

Abstract

Objective. Alloys based on AgMn are being evaluated in our laboratory for their possible use as an alternative to Type III dental alloys. They respond to heat treatment and develop hardness values comparable to that of Type III alloys. The objective of the present research was to evaluate their corrosion characteristics.

Methods. The three experimental silver-based alloys of the following composition (at%): (1) 63Ag37Mn, (2) 60Ag35Mn5Au and (3) 60Ag35Mn5Pd, were tested in their peak-hardened condition. Following 0.5h open-circuit potential (OCP) measurement of each alloy in a phosphated buffer saline (PBS) solution, its current–potential profile was generated by the cyclic voltammetry technique within −1300 and +200mV (SCE) at 1mVs⁻¹. In a separate test, the OCP of each alloy was monitored over a 24h period.

Results. Each of the three alloys showed ennoblement of their OCP over time due to dissolution of Mn and consequent enrichment with Ag (Au or Pd). At 24h, the two ternary alloys were the most noble followed by the binary alloy. With respect to the cyclic voltammetry, oxidation of Ag was noted during forward scans at around 0mV. The reverse scan was associated with a reduction current peak between −37 and −128mV. The values for this peak, which is a measure of Ag oxidation, were highest (11.5mAcm⁻²) for the binary alloy followed by the Au- (2.9mAcm⁻²) and Pd-containing (0.04mAcm⁻²) alloys, respectively. This indicates that, for equivalent concentration, Pd is more effective in reducing Ag corrosion than Au.

Significance. Alloys based on the AgMn system are as hard as Type III dental alloys. Information on the corrosion characteristics of the AgMn-based alloys presented here is of value in further development of this alloy system.