Only the most accomplished weapon-smiths can alloy a “silvered weapon” – mostly Ducateon, some few other groups that have been taught or learned the process. Silvered Weapons of the Steel Realms have a particular quality of being able to resist the effects of Ironrot. Most can silver a weapon temporarily with a soft coating. In such cases, a weapon must have the silvering process re-applied after a certain amount of Major [Hits]. Greeniron has the same properties, though there is none of its source material left to make any further items.
Northern Merchant Cities has a special developed Crafting of the North Merchant Cities that anodizes and anneals Silvered blades to have a stronger silver coating. They need less work over time to stay useful, but cost more up front and only the highest quality and heat forges of the Steel Realms can do so.d20 [specific] Requirements: Per PHB ™