Impeccable raw material. The raw material base is the stainless steel 18/10. This number is the quality seal of Riva objects, and refers to the metal composition: 18% chromium and approximately 10% nickel. The oxygen, when combined with chromium forms a thin chromium oxide layer on its surface, which gives the stainless steel a high resistance to corrosion. Therefore, the better the polishing of a workpiece the more its surface is in contact with air and consequently more resistant to oxidation.