Tarnish vs Corrosion — MFDS Part 1 MCQ
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Correct answer: A — Tarnish describes visible surface discolouration, whereas corrosion describes chemical or electrochemical degradation of the alloy.
Explanation lettering: D = shown as B · B = shown as C · C = shown as D
A is correct. Tarnish is an appearance-based term describing loss of lustre or visible surface discolouration, commonly associated with a surface film or reaction products. Corrosion is the chemical or electrochemical degradation of the alloy and may cause ion release, dissolution and deterioration of its properties. Tarnish can accompany corrosion, so it should not be defined as invariably occurring without any material loss. Option B reverses the concepts. Option C confuses tarnish with mechanical wear and incorrectly excludes chemical change. Option D is false because neither process is confined exclusively to noble or base-metal alloys. Option E is incorrect because tarnish and corrosion describe related but distinct phenomena.
Reference: Marek M. Interactions between dental amalgams and the oral environment. Advances in Dental Research. 1992;6:100–109. https://pubmed.ncbi.nlm.nih.gov/1292448/