You’ve undoubtedly held or at least seen something that has been through the passivation process because passivation is a technique that places a light coat of material – such as metal oxide – on a material to protect it against corrosion.
While passivation takes place only under certain conditions and often is used most often to preserve and strengthen metals, it’s also used in microelectronics to enhance silicon.
The term passivation comes about because the process returns the metal material or stainless steel back to its original specifications (it becomes “passive”) as it removes unwanted oils and debris from the metal’s surface. In short, the metal is less affected by corrupting environmental factors.
Passivation is needed because once a part is machined, a number of particles can infiltrate the base metal’s surface, thus lessening its resistance to corrosion and making it less able to withstand the onslaught of environmental factors such as dirt, debris, free iron residue, grease and machining oils. Without passivation, these elements could embed themselves in the surface of the metal’s surface during the machining process.
The human eye often misses minute particles of residue, grease, oils, and so on and they can then go on to weaken the part.
But passivation improves the part’s surface, with the newly restored surface working as a protective coating against the factors mentioned above as well as extreme environments, water and even air.
Passivation doesn’t change the base metal’s outward appearance.
In conclusion, the advantages of passivation include the restoration of a smooth and uniform finish, greater resistance to corrosion and an extension and improvement to the life of the metal.