Sea water has the potential to corrode both ferrous and non-ferrous metals through a number of chemical and electrochemical processes. The combination of oxygen, dissolved inorganic salts - particularly chloride anions – and different grades of metals all submerged in water, provides an ideal environment for corrosion.
Vulcan Seals has been a leading manufacturer and supplier of Mechanical Seals to the marine shipping industry for over 25 years. In that time our 304-grade stainless steel seals have been successfully used in hundreds of different marine applications with proven reliability and resistance to sea water corrosion. Combined with our product range, design and construction quality, we have become the Mechanical Seal brand of choice for a number of major marine industry companies.
In around the 1960s, 304 stainless steel did carry some poor reputation for sea water applications due to the main metal parts being supplied in their natural machine-finished state.
The image above shows a 1980s seal spring with the rough surface finish which increased the surface area open to anionic corrosion from the chloride anions in sea water. The resulting rust led to the bad reputation.
To reduce the corrosion issue, supplying more expensive 316 stainless steel, brass or Monel® parts became common practice and the end-user marine industry began to move away from 304 stainless steel.
Regardless of end-use, all metal components used in Vulcan Mechanical Seals are routinely electropolished.
This smooth polished surface finish, combined with the higher quality of modern 304 stainless steel, minimises sea water corrosion and removes the need to specify higher cost materials.
Although the Vulcan Type 1742S above (left) has not been cleaned, the uncorroded electropolished 304 stainless steel can still be seen after a long, reliable service in a bilge pump. The brand new seal of the same type on the right demonstrates the standard Vulcan Seals electropolished surface finish.
Corrosion can still occur inside sea water equipment where several differing metals are present. Anodic or electrochemical corrosion of the pump components or Mechanical Seal can be severe regardless of the grades used.
In such cases, using 304 or 316 stainless steel as standard for all internal pump components removes the chance for anodic corrosion as the metal grades are the same. Mixing 304 and 316 or similar grades is usually not problematic.
Vulcan Seals is continually improving the performance and quality of its Mechanical Seal range to suit industry and market demands. For more information, please use the contact form on this page or email us directly: firstname.lastname@example.org
Disclaimer: All technical information provided is for guidance only. Product performance is dependent on many factors including materials and other operating conditions. ® All product names and brands used are for identification and reference purposes only, and do not imply endorsement nor affiliation.
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