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Some metal parts have to be machined in a special way if the intended use will require weather resistance attributes or the prevention of wear and tear.  It is also important to know if the material to be used has to meet certain specifications for further manufacturing such as welding.  The staff of PF CNC Machining also cares about whether the part may also need to be suitable to be paired with other metals as in the case of nuts and bolts. 


Take stainless steel for example, it is noteworthy for being inoxidizable.  It is a steel alloy with a minimum of 10% chromium content by mass.  It is corrosion resistant, and it is largely used for food handling and cutlery among other purposes because of it’s resistance to rust.  Chromium is the element in stainless steel that makes stainless steel corrosion resistant.  Stainless steel does not readily corroderust or stain with water as ordinary steel.  It is worth to note that any metal is susceptible to stain in low-oxygen, high-salinity, or poor air-circulation environments.  There are various grades and surface finishes of stainless steel to use, where the properties of both steel and corrosion resistance are required.


Stainless steel is different from carbon steel by the amount of chromium present in it.  With that in mind one must be careful with the coolant used to machine it, and not contaminating it with other metals.  Using tools on stainless that have been used before on other metals, may cause your stainless to be contaminated and become prone to stain.


Unprotected carbon steel rusts readily when exposed to air and moisture.  This iron oxide film (rust) is active and accelerates corrosion by making it easier for more iron oxide to form.  Since iron oxide has lower density than steel, the film expands and tends to flake and fall away.  In comparison, stainless steels contain sufficient chromium to undergo passivation (becoming "passive," less affected or corroded by the environment), forming an inert film of chromium oxide on the surface. This layer prevents further corrosion by blocking oxygen diffusion to the steel surface and stops corrosion from spreading into the bulk of the metal.


Passivation occurs only if the proportion of chromium is high enough and oxygen is present.  With this in mind the experienced machinist would not change the chromium proportion of stainless by grinding it with a tool that was used to grind carbon steel.  When sanding paper is used on carbon steel, small particles stay on the paper and can be transferred to stainless.  That physical change can then alter the content of the alloy to one that will no longer be stainless.


If you have stainless steel material to machine and you need a machining service quote, please contact us.  We will be happy to assist!

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