Stainless steel has always been the ideal choice for impellers due to its surface properties, overall strength and long service life. But bronze was the industry standard for years – based on economy of resources, ease of manufacturing and its lighter weight helping facilitate hydraulic performance. Bronze is durable Use of stainless steel was typically reserved for specialty facilities and custom projects because it was simply cost prohibitive. With advances in manufacturing technology, stainless steel has become a more viable option. And in many cases, stainless steel impellers represent a better value because they are less likely to incur costly repairs due to corrosion and abrasives.

Making Hard Choices

Although metal hardness isn’t the only criteria of resistance to abrasive wear, metal hardness does provide a convenient index in selecting the option that best fits your manufacturing application. Here is a list of common materials from which impellers are made – listed in order of increasing abrasive-wear resistance:

  • Cast iron
  • Bronze
  • Manganese bronze
  • Nickel-aluminum bronze
  • Cast steel
  • Stainless steel

Breaking from Tradition and Fighting Corrosion

You just don’t get the same corrosion resistance from bronze that you’ll get from stainless steel. The surface characteristics of bronze cause it to wear faster over time. And alloys commonly used to reinforce bronze impellers are susceptible to dezincification – which dissolves the zinc and degrades the metal. 303- and 304-grade stainless steel impellers are specified for all but the most highly corrosive applications. 

While there may be some extreme applications with very high chemical concentrations where stainless steel is not appropriate, stainless steel can be used in a number of 

applications that do involve acid and alkali. In fact, 316-grade stainless steel impellers are used exclusively for food and drug applications. While there are specialty grades of bronze that comparable corrosion resistance, they’re more difficult and more expensive to manufacture.

Consider the Long-Term Value

When you’re choosing and impeller, consider the long-term value of stainless steel over other metals. Consider the following:

  • Application
  • Strength
  • Corrosion resistance
  • Abrasive-wear resistance
  • Cavitation erosion resistance (wear of hard vs. soft metals)
  • Overall cost

Stainless steel delivers greater durability, improved surface characteristics that result in improved sustainable hydraulic performance and energy efficiency, improved chemical resistance and application flexibility, reduced corrosion or degradation potential, enhanced consistency between impellers, easy clean up and reduced maintenance cost. That adds up to a longer service life and a better overall value. 

Let the mixing equipment specialists at Fawcett help you find the precise solution that works for your mixture requirements. For over half a century, Fawcett Mixing Equipment Specialists has looked at new ways to improve quality, maximize efficiency, and minimize safety concerns to find solutions for a variety of mixing applications. [CONTACT INFO]