Classification of Impeller Materials for Marine Pumps

I. Metal Materials

1. Cast Iron

Types: Gray cast iron (HT series), ductile iron (QT series).

Features: Low cost, moderate wear resistance; susceptible to seawater corrosion but suitable for freshwater or mildly corrosive media.

Applications: Bilge pumps, freshwater cooling pumps, and auxiliary pumps in non-seawater environments.

2. Stainless Steel

Grades: 316L, 904L, 2205 duplex stainless steel.

Features: Excellent seawater corrosion resistance, high strength, and good resistance to pitting/crevice corrosion.

Applications: Seawater pumps, ballast pumps, and main cooling pumps in marine environments.

3. Copper Alloys

Types: Nickel-aluminum bronze (NAB), brass (Cu-Zn alloy), bronze (Cu-Sn alloy).

Features: Superior seawater corrosion resistance, excellent cavitation resistance, and good wear resistance.

Applications: Main seawater pumps, propeller shaft pumps, and cargo pumps in chemical tankers.

4. Nickel-Based Alloys

Examples: Hastelloy C-276, Inconel 625.

Features: Resistant to strong acids, alkalis, and high-temperature media; ideal for extreme corrosion conditions.

Applications: Pumps for transporting aggressive chemicals or high-temperature fluids on special ships.

5. Titanium Alloy

Features: Exceptional seawater corrosion resistance, high strength-to-weight ratio, and resistance to chloride-induced stress corrosion.

Applications: High-end marine applications (e.g., military vessels, deep-sea exploration ships) and pumps in harsh offshore environments.

II. Non-Metallic Materials

1. Engineering Plastics

Types: Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP).

Features: Lightweight, excellent chemical resistance (especially to acids and solvents), and low friction.

Applications: Chemical tanker pumps, bilge pumps for corrosive media, and pumps in food-grade marine applications.

2. Ceramic Materials

Types: Silicon carbide (SiC), aluminum oxide (Al₂O₃), zirconia (ZrO₂).

Features: High hardness, wear resistance, and corrosion resistance; suitable for particle-laden fluids.

Applications: Slurry pumps for dredging ships, ballast water treatment pumps, and high-wear environments.

3. Composite Materials

Examples: Fiberglass-reinforced plastic (FRP), carbon fiber composites.

Features: High strength, corrosion resistance, and cost-effectiveness compared to metals.

Applications: Auxiliary pumps on small vessels, non-corrosive fluid transport systems.

III. Special Alloys and Coatings

1. Duplex Stainless Steel

Features: Combination of high strength and corrosion resistance, ideal for high-pressure marine pump applications.

Applications: High-head seawater pumps, offshore platform circulation pumps.

2. Surface Coatings

Types: Ceramic coatings (e.g., plasma-sprayed Al₂O₃), thermal spray metal coatings (e.g., Stellite).

Features: Enhance wear and corrosion resistance for existing impellers, suitable for maintenance and upgrading.

Applications: Retrofit of older marine pumps to extend service life in abrasive/seawater conditions.

IV. Selection Considerations for Marine Impellers

Environmental Factors:

Seawater corrosion: Prioritize stainless steel, copper alloys, or titanium.

Abrasive media: Use ceramics, hard alloys, or coated surfaces.

Operational Conditions:

High temperature/high pressure: Choose nickel-based alloys or duplex stainless steel.

Chemical compatibility: Select PTFE or PVDF for strong acids/alkalis.

Regulatory Compliance:

Meet marine standards (e.g., ABS, DNV GL) for material certification in critical applications.

By matching impeller materials to marine operational demands, ships can ensure pump reliability, minimize maintenance, and adapt to harsh offshore environments.