XG 14/12 Large Gravel Pump in Seawater Intake for Desalination: Copper‑Nickel Alloy Coating Solution for Biofouling Prevention

📌 Key insight: Traditional antifouling methods (chemical injection, electrolysis) have drawbacks. 90/10 copper‑nickel alloy coating provides intrinsic, long‑term biofouling protection without environmental impact or external power.

Introduction

In seawater intake for desalination plants, the intake pumps face two major challenges: high salinity / chloride corrosion, and marine biofouling – the attachment and growth of barnacles, mussels, algae, etc. on wetted surfaces. Biofouling leads to reduced flow, lower efficiency, increased vibration, and eventually blockage or even pump seizure.

The XG 14/12 is an extra‑large gravel pump in the XG series (350mm inlet, 300mm discharge), offering flow rates up to 3,200 m³/h and heads up to 60 m. With its single‑casing, clamp‑connection design, it is ideal for high‑volume slurry transport. However, its complex flow passages and large wetted area make it particularly vulnerable to biofouling when used in seawater intake.

Based on extensive experience in seawater pump antifouling, Hebei Xingou Machinery Equipment Co., Ltd. provides a copper‑nickel alloy (90/10 Cu‑Ni, C70600) coating solution – delivering both corrosion resistance and inherent biofouling prevention. This article analyzes biofouling mechanisms, compares various technologies, and details the implementation, technical key points, and economics of the copper‑nickel coating for the XG 14/12 pump.

1. Biofouling Problem in Seawater Intake Pumps

1.1 Biofouling Development

Biofouling is a multi‑stage process: organic molecules adsorb within seconds, bacterial attachment within hours, microalgae within days, and macro‑foulers (barnacles, mussels) within weeks to months. Areas with low flow velocity, dead zones, and welds are the most susceptible.

1.2 Specific Damage to XG 14/12 Gravel Pump

• Single‑casing design – The metal body directly contacts seawater; no outer protective layer.

• Clamp connections – Joint crevices are hotspots for attachment.

• Complex flow passages – Low‑velocity zones promote rapid settlement.

• High flow rate – While continuous flow provides some self‑cleaning, it also transports larvae into the pump.

Biofouling can reduce pump efficiency by 5%‑15% per year, and severe cases require shutdown for cleaning, interrupting water supply.

2. Comparison of Antifouling Technologies

Table 1: Comparison of antifouling methods for XG 14/12

2.1 Why Chemical Injection Is Not Ideal

For standby pumps, high‑concentration biocide can remain undiluted and cause severe corrosion of filters, suction pipes, and pump internals. Additionally, environmental regulations increasingly restrict high residual chlorine discharge.

2.2 Electrolytic MGPS

Marine Growth Prevention Systems (MGPS) use electrolysis to generate copper and aluminium ions, achieving >96% antifouling efficiency. However, for the XG 14/12’s large, complex flow passages, multiple anodes are needed for uniform coverage, increasing complexity and maintenance.

3. Copper‑Nickel Alloy Solution: Why 90/10 Cu‑Ni (C70600)

3.1 Unique Antifouling Mechanism

90/10 copper‑nickel alloy releases copper ions (Cu⁺) at a very slow, steady rate, forming a complex protective film (oxides, chlorides, hydroxy‑chlorides) on the surface. This film makes the surface inhospitable for most marine organisms, providing intrinsic biofouling resistance.

In clean, aerated seawater, 90/10 Cu‑Ni exhibits excellent uniform and localized corrosion resistance, with a typical corrosion rate as low as 0.002 mm/year.

3.2 Technical Aspects of Coating / Cladding

For the XG 14/12, two application methods are available: thermal spray coating or thin sheet cladding. The alloy must freely contact seawater to form its protective film; cathodic protection must be avoided as it destroys the antifouling capability.

Design flow velocity up to 3.5 m/s is acceptable, well within the pump‘s normal operating range.

3.3 Field Validation

Exposure tests at Langstone Harbour, UK, showed that freely exposed (non‑cathodically protected) copper‑nickel panels remained clean except for a thin biofilm, while cathodically protected panels fouled similarly to mild steel. This confirms that cathodic protection must not be applied to copper‑nickel coated surfaces.

Over 50 years of service in marine applications (pipework, condensers, platform splash zones) have proven the reliability of 90/10 Cu‑Ni.

3.4 Corrosion Resistance vs. Stainless Steel

316L stainless steel is susceptible to crevice corrosion, stress corrosion cracking, and lacks inherent antifouling properties. In high‑velocity zones (impeller inlet, discharge corner), copper‑nickel offers superior erosion‑corrosion resistance.

4. Implementation Plan for XG 14/12 Gravel Pump

4.1 Coverage Scope

4.2 Coating Procedure (Thermal Spray)

4.3 Critical Points

• No cathodic protection – The Cu‑Ni coating must remain freely exposed to seawater to form its protective film. Any CP will ruin antifouling performance.

• Avoid galvanic contact with less noble metals – Direct contact may cause accelerated galvanic corrosion.

• Film maturation period – The protective film naturally forms over 6‑8 weeks. Avoid shutdown during this initial period.

• Flow velocity – Design velocity ≤3.5 m/s is acceptable.

• Local repair – Damaged coating can be repaired by weld overlaying or cold spray of Cu‑Ni powder.

5. Cost and Economic Benefit

Estimated for one XG 14/12 pump (based on actual project costs):

Payback period: Initial investment $40k‑$60k, annual saving $11k‑$20k → 2‑3 years. Given the pump‘s expected service life of 20‑30 years, the life‑cycle benefit is immense.

6. Case Studies

Middle East large desalination plant (500,000 m³/day): The intake pump station used XG‑type gravel pumps. Previously, chemical injection cost $120,000/year and required biannual shutdowns for cleaning. After switching to 90/10 Cu‑Ni coating, no significant biofouling was observed after 24 months, pump efficiency remained above 95%, and the solution was rolled out to six other pumps, reducing total operating cost by ~40%.

Offshore platform seawater lift pump: Severe barnacle and mussel attachment required impeller cleaning every 3 months. After 90/10 Cu‑Ni cladding, the pump body remained free of macro‑fouling after 5 years, the impeller retained its original profile, and payback was achieved in 18 months.

Global statistics: According to the International Copper Association, 90/10 copper‑nickel alloy has been reliably used in marine engineering for over half a century, with cumulative global usage exceeding 1 million tonnes. It is recognized as a highly cost‑effective material for seawater pumps, piping, heat exchangers, and splash‑zone cladding.

7. Conclusion

The XG 14/12 large gravel pump faces severe biofouling challenges in desalination seawater intake. Traditional methods (chemical injection, electrolysis) have limitations. The 90/10 copper‑nickel alloy (C70600) coating/cladding solution provides inherent biofouling prevention through steady copper ion release and excellent seawater corrosion resistance, offering a “one‑time investment, long‑term benefit” approach.

• Apply 90/10 Cu‑Ni to all wetted parts of the XG 14/12 via thermal spray or sheet cladding.

• Never apply cathodic protection to the coated surfaces; allow the natural protective film to form.

• Allow ~6‑8 weeks of continuous operation after first commissioning for film maturation.

• Initial investment $40k‑$60k, payback 2‑3 years, significant lifecycle savings.

Hebei Xingou Machinery Equipment Co., Ltd. provides design, application, and on‑site technical guidance for copper‑nickel alloy coating on XG series gravel pumps. For evaluation or a custom quote, please contact our technical team.