What is difference between silver oxidation and corrosion

A. Iridite 18-P is a chromate conversion coating for silver that provides tarnish and oxidation protection. This product is available from Macdermid Waterbury CT. There may be other suppliers of chromates, but I am not aware of them. The film may be somewhat yellow, and offers good protection against tarnish and oxidation. The coating does not interfere with electrical contact.

A. The black or blueish color on the silver is not a oxide layer. When you are oxidizing silver you use f.ex. potassiumsulfide (K2S). The sulfide react with the silver and make a silversulfide layer - which is black/blueish... So it's not a really oxide layer, but a layer that is created throug an redox proces.

Hope it answer some of your question... :)

A. Hi Oliver. It's easy to appreciate the frustration, but it's difficult to resolve it because "corrosion" is such a complex issue...

• Things that are corrosion resistant in one environment are not necessarily corrosion resistant in another. For example, zinc plating is the most popular metallic corrosion-proofing coating for steel components in typical ambient conditions, but it offers absolutely zero protection in acid situations. So, do we mean resistant to acids, alkalies, and other chemicals, or do we mean resistant to rain?

• Whether a metallic coating contributes to corrosion resistance depends what substrate you are putting it on. This is because some metals are sacrificially protective to others. One reason zinc is so popular, besides its cost, is that it sacrificially protects steel from corrosion even if pinholes exist in the coating -- just as a zinc anode protects a steel ship hull. But when silver is applied to steel the result is the opposite: if any pinholes exist, the silver forces the steel to sacrifice itself to protect the silver.

• Often it is not the metal which is corrosion resistant, but the corrosion products from the initial corrosion. Metals like aluminum and titanium are corroded extremely easily but the corrosion products tend to form a fairly tight and adherent coating that slows down any additional corrosion whereas the corrosion product of steel (rust) is powdery, non-adherent, absorbs water, and accelerates continuing corrosion instead of reducing it.

• Sometimes we disagree on what constitutes "acceptable" corrosion. Silver tends to not stay tarnish-free. Do you need a tarnish-free surface, or do you not care what it looks like?

When all this is taken into account, it's difficult to say if silver coating is corrosion resistant. In general, I'd say yes because silver plated flatware can last decades; but it will probably tarnish quickly. Good luck.

Regards,

A. In normal storage silver is very adept at reacting with sulfur in the air to tarnish through many colours depending on the atmosphere to grey black. Silver sulfide.
This can be removed by a number of solvents e.g. sodium sulfide, acidic Thiourea [on eBay or Amazon], Al foil in alkaline conditions, rubbing polish, etc. Chromate dipping can resist this discolouration as can organic sulfur compositions as in various silver polish formulations such as Goddards who had patents but now run out.
Don't know if this what you're asking but please clarify