The stainless steels are basically alloys of chromium and iron. When chromium, a metallic element, is added to iron in excess of 10% it imparts throughout the entire body of the metal remarkable resistance to corrosion and heat. Other elements are added to the iron-chromium, combination to obtain special characteristics.. The most important of these is nickel, which is used to produce 18-8 that is, 18% chromium, 8% nickel, balance iron. Other useful additions are molybdenum, columbium, titanium, sulfur, and selenium, all of which result in modifications for special service or fabrication.
Type 304 stainless steel This grade of stainless steel is characterized by a low carbon and high chromium and nickel content. This results in high strength with excellent stability and corrosion resistance, and is easily formable and weldable and is suitable where the finish product must resist corrosion. The "all purpose" stainless steel.

Type 316 stainless steel The addition of molybdenum gives this grade of stainless steel a generally greater resistance to corrosion . This extra measure of corrosion resistance makes this grade particularly suitable for applications involving severe corrosive conditions. It is more resistant to marine atmospheres.

"L" grade stainless steel Type 304L and type 316L are specialized alloys that have an extra low carbon content which helps eliminate the hazard of carbide precipitation during welding. This increases the corrosion resistance of these grades at the weld seam. Use of this alloy is reserved for special corrosion problems where extensive welding is to be done.

SMI offers several standard finishes which can be applied to meet your application requirements

DURO-SAN Internal welds ground and polished (#3 polish) External welds wire brushed Internal and external sheet surfaces as described below (from 2b to #4 polish)

PHARMA-SAN Internal and external welds ground and polished (#4 polish) Internal And external sheet surfaces as described below (from 2b to electropolish)

WELD FINISH
Wire brushed This finish is not flush and will contain irregularities on the remaining weld. When compared to all the abrasive finishing methods this process results in the least amount of weld material removed
Ground & Polished Welds ground and ribbon polished to blend with the sheet finish, #3 Polish or better

SHEET FINISH
#2b As received from the mill Hard and dull, rolled finish
#3 polish 80-l20 Grit (50-80 rms) The weld will be ground flush and discoloration will be removed This surface is a near sanitary finish. Pits and defects are minimized
#4 polish l20-l50 Grit (30-40 rms)
The weld is ground flush with all pits and defects removed. This finish is normally used for food, dairy and sanitary applications #7 polish 320 Grit (5-l0 rms) A very fine finish buffed with a rouge to attain reflectivity. Used in highly corrosive or sterile environments.


ELECTROPOLISH
This electrochemical process for providing product surface integrity beyond available conventional mechanical finishes is provided in a range from 150 grit finish to 320 grit finish. Electropolishing SMI vessels obtains improved corrosion resistance by reducing the exposed surface area, removal of metallic and non-metallic surface inclusions, obtaining a smooth releasable surface for improved cleanability . The resulting surface is effectively passivated with the resulting chrome oxide film reformed to a maximum obtainable thickness.
  © 2005 Innovative Technology Partners