Corrosive Resistance

The marine grade stainless steel which we use has 22% chromium. A chromium film forms once exposed to oxygen providing an elevated defiance to corrosion by creating a passivation layer. In the context of corrosion passivation is the spontaneous formation of a hard non-reactive surface film that inhibits further corrosion. This layer is usually a few atoms thick. This invisible film on the surface of the metal protects against a wide range of corroding agents.

Corrosion is the breaking down of essential properties in a material due to chemical reactions with its surroundings. The spontaneous formation of the chromium film prevents this from happening.

Pitting corrosion is an extremely localised corrosion where a corrodent like sodium chloride in sea water creates a small hole in the metal due to a lack of oxygen around a small area as well as the corrodent being stagnant. It's extremely insidious and causes little sign on the surface of the metal but damages the deep structure. The chromium film creates a barrier against this happening.

Atmospheric dirt and dust particles can come from various sources, soil/fertilizer dust lifted by the wind, volcanic smoke and general pollution caused by motor cars etc. The dust particles which settle on houses increase the breakdown of a lot of metals and the formation of rust. The passivation layer of chromium oxide on stainless steel precludes rust formation. If you see red rust forming it is probably due to some iron particles that have contaminated the surface of the stainless steel and it is these particles which are rusting. These particles can be removed with water.

Stress corrosion is a position on an object where stress is concentrated in one area. The carbon content in stainless steel makes it an ideal choice for guttering as it toughness means it won't crease under ladder pressure or general handling when removing or reinstalling due to modification being done to houses.