A variety of metal polishing services is available in the market. Choosing the right type of finish will depend on the stainless steel alloy being used and the purpose of the stainless steel. For example the stainless steel used in the medical industry and the one used in a manufacturing plant will be polished with very different finishes. Roughened finishes might not be the best option in ready-to-use applications. Rough finishes are used to prepare the surface for additional polishing or other treatments.
Ra or Roughness Average is the commonly used term to quantify the level of roughness of stainless steel surface. It is used to measure the height of the roughness from a mean line. An average between the peaks and valleys of the surface is taken to calculate the roughness average of a surface. Ra is denoted by micrometers (µm) or micro-inches (µin). It is a common parameter used to denote the roughness of a surface making it easier for transactions to take place.
One of the popular finishes is the Ra 30 surface finish or the #4 finish. It is also known as satin finish. It is an electronic polishing method and produces very low roughness. Hence, it is a very fine finish used in a variety of industries. It exhibits a 180-grit grain, which renders a dull finish. The absence of a mirror-like finish make sit perfect for use in sanitary environments like in the medical industry. The grain is produced in a single direction giving the surface a smooth yet dull feel. This metal polishing technique provides excellent corrosion resistance. It is used in high purity applications like sanitary and pharmaceutical products.
Extensive tests have been conducted that verify the importance of smooth finishes. The surface finish affects the corrosion and abrasion resistance that stainless steel exhibits. Hence, the finish needs to be customized according to the industry and the environment in which it is used. Thus, the type of surface finish chosen will make a difference in the life of the application.