The nitric acid test is not suitable for gold coatings less than 0,6 micrometres thick, for coatings less noble than gold or platinum, or for gold-flashed palladium and its alloys
ICS
25.220.40 Metallic. Including electrolytic depositions, cathodic coatings, autocatalytic coatings, etc. / Металлические покрытия. Включая электролитическое осаждение, катодные покрытия и т.д.
