Aluminium Bronze alloys: an alternative for pumps in marine applications
When it comes to working in an industrial, maritime environment, the challenge is to design reliable and long-lasting equipment. For a long time, steel and stainless steel have been considered the only solution despite a low corrosion resistance. Inoxyda has specialized in developing alternative solutions based on aluminium bronze alloys, which have excellent resistance to seawater corrosion but not only.
Properties of Aluminium bronze alloys developed by Inoxyda
Aluminium Bronze is a family of copper-based alloys including aluminium, nickel, and iron; each component is adjusted to improve strength, corrosion resistance, and/or machinability and is then identified by different grades according to international standards (ex: EN 1982 / ASTM /ASME):
- High mechanical strength
- Density (5 % lighter than steel)
- Low magnetic permeability (of <1.03µ in selected grades)
- High Corrosion resistance (marine-based corrosions)
- Good stress corrosion properties
- Good cryogenic properties
- Lower cost than Titanium
Machined NAB alloy impeller (credit Inoxyda)
The main property comes from its protective oxide surface film, which can self-repair and is therefore a better solution in the long run, compared to any coated steel.
Biofouling resistance is another characteristic of aluminum bronze alloy, which is often ignored; unlike other standard metals, copper ions’ slow dissolution prevents organic elements from developing.
When dealing with pump applications, resistance to cavitation is an essential design criterion; cavitation results from small water vapor bubbles formed at low-pressure points, causing erosion at the point of contact, which in some extreme cases damages the blades. Nickel Aluminum Bronze provides excellent resistance to this phenomenon, explaining why NAB alloys are widely used in the shipbuilding industry, including for propellers.
All those interesting properties are further developed in the Guide to Nickel Aluminum Bronze for Engineers, published by Ivan Richardson and the Copper Development Association.
Comparison of average cavitation resistance (credit Inoxyda)
Application to pumps for seawater service
Pumps used for seawater service face severe corrosion issues for which the use of Aluminium Bronze alloys is a solution. They are available using various casting processes: sand casting, centrifugal casting, or continuous casting, thus offering opportunities to manufacture various engineered pump components such as:
- Pump casings (split pump, centrifugal, volute)
- Impellers (closed, open, fish-friendly)
- Suction casings or diffusers
- Discharge elbows
- Riser columns
- Thanks to large in-house capacities, we can cast above components up to 4m X 4m, and 8to finished machined weight.
Split Pump aluminium bronze (credit Inoxyda)
Inoxyda’s knowhow: a solution for seawater applications in Nordic applications
Nordic countries are historically and geographically linked to the sea; thus, the maritime industries play a significant role in the countries’ economies. Inoxyda has provided aluminium bronze castings to Scandinavia’s critical players in cooperation with Hj. Edwards & Co. AB, a Gothenburg company, focusing on engineered applications and supporting customers with world-class suppliers for more than 100 years.
Contact Edwards for more information about Inoxyda’s Aluminium Bronze Castings: