Everything you want to know about passivation

  • Published on
    03-Mar-2017

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NADCAP certified passivation refers to a common but extremely important procedure that is used during the manufacture of stainless steel components. When talking about passivation the emphasis is paced both on the actual process as well as that type of characteristics that it imparts. A lot of care usually has to be taken because a great deal of damage can easily occur if any of the components are not handled correctly whether it is during their transportation or storage. You can understand this fragility if you know how the process of NADCAP certified passivation takes place as well as what it does. Even though passivation can occur on its own on some forms of stainless steel, the NADCAP certified passivation process was developed so as to make sure there is a sort of infirmity in the process.

The NADCAP certified passivation process involves the use of an oxidizing agent like nitric acid so as to create a film layer that is basically a few atoms thick. Since such a layer is chemically inert it will basically reduce the reactivity of stainless steel. As soon as the process of passivation has been accomplished, some additional machining will easily remove that thin layer that will have been created during the procedure. This removal will not simply occur on the surface that was worked upon but also on the flying chips of the material whether it is from a cutting tool or the part that will become damaged in other regions where they could land or ricochet.

In addition to the mechanical removal of NADCAP gold electroplating that could come as a result of re-machining, cutting fluids that are normally applied to reduce the damage caused by heat as well as flushing away the chips are also bad news to this thin layer. It is a common occurrence for sulfides or any other chemicals that are used in those cutting fluids to actually enhance the release of chips away from the cutting area. Such compounds will actually further weaken the passivation layer and penetrate it thereby initiating the process of corrosion; if any of these happenings are suspected it is preferable that re-passivation is considered.

It is also important to remember that as a matter of fact, any parts that have gone through the process of NADCAP metal finishing should not under any circumstances be heat treated. The process of heat treating will definitely alter the crystalline structure of the metal and which will affect its strength, hardness, elasticity and ductility. While it may appear for many that stainless steel parts have the innate ability to handle any kind of handling process, it is good to note that the NADCAP certified passivation layer is very fragile and can easily come off.

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