Thread: stainless steel ?

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Not a metalurgist, but I do know stainless will rust. We had this argument from customers in the boat business for years now........they buy a boat and accuse the mfr of using cheap stainless because it rusted. We had to explain it is stain-LESS, which means it will still rust, only more slowly. They somehow thought they never ever had to do any maintenance on it to keep it shiny.

Don


Stainless steel
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The 630 foot (192 m) high, stainless-clad (type 304) Gateway Arch defines St. Louis, Missouri's skyline.
The 630 foot (192 m) high, stainless-clad (type 304) Gateway Arch defines St. Louis, Missouri's skyline.

In metallurgy, stainless steel is defined as an iron-carbon alloy with a minimum of 10.5% chromium content.[1] The name originates from the fact that stainless steel does not stain, corrode or rust as easily as ordinary steel (it "stains less", but is not actually stain proof). This material is also called corrosion resistant steel when it is not detailed exactly to its alloy type and grade, particularly in the aviation industry. As such, there are now different and easily accessible grades and surface finishes of stainless steel, to suit the environment to which the material will be subjected in its lifetime. Common uses of stainless steel are everyday cutlery and watch straps.

Stainless steels have higher resistance to oxidation (rust) and corrosion in many natural and man made environments; however, it is important to select the correct type and grade of stainless steel for the particular application.

High oxidation resistance in air at ambient temperature is normally achieved with additions of a minimum of 13% (by weight) chromium, and up to 26% is used for harsh environments.[2] The chromium forms a passivation layer of chromium(III) oxide (Cr2O3) when exposed to oxygen. The layer is too thin to be visible, which means that the metal remains lustrous. It is, however, impervious to water and air, protecting the metal beneath. Also, this layer quickly reforms when the surface is scratched. This phenomenon is called passivation and is seen in other metals, such as aluminium and titanium. When stainless steel parts such as nuts and bolts are forced together, the oxide layer can be scraped off causing the parts to weld together. When disassembled, the welded material may be torn and pitted, an effect that is known as galling.

Nickel also contributes to passivation, as do other less commonly used ingredients such as molybdenum and vanadium.