When customers ask whether a pump is suitable for seawater or brackish water*, everything comes down to choosing the right materials and understanding corrosion processes. Here we will explore what seawater does to pump materials, how global differences affect corrosion, and when standard BBA Pumps equipment is or is not suitable for saltwater applications.

What is seawater?

Seawater consists of approximately 96–97% water and the balance is made up of dissolved salts, minerals and small amounts of organic matter. The average salt content (salinity) is roughly 3.5%, giving seawater a density of about 1025 kg/m³ - higher than that of freshwater. Salinity varies by location, depending on evaporation rates and freshwater inflow from rivers.

Temperature influence on corrosion rate

Temperature has a direct impact on corrosion speed. As a rule of thumb, every 10 °C increase can approximately double the rate of corrosion, depending on oxygen concentration. This means corrosion varies strongly by climate zone:

• Cold seawater (5–15 °C) - lower corrosion rates but often higher oxygen content, which can still accelerate corrosion.
• Tropical seawater (25–35 °C) - faster chemical reactions cause significantly higher corrosion rates.
• Fluctuating temperatures - seasonal or tidal changes add mechanical stress due to thermal expansion and contraction, exposing materials to alternating corrosion conditions.

Not every material is suitable for continuous exposure to seawater, especially in warm, high-salinity environments.

Global differences in seawater corrosivity

For rental and offshore operations worldwide, it’s important to know that not all seas are equally corrosive. Factors such as temperature and salt concentration affect the service life of pump materials.

Less corrosive environments: 

• Baltic Sea - low salinity (7–10 g/l), similar to mild brackish water.
• Arctic waters - low temperatures significantly slow corrosion.

Moderately corrosive environments: 

• North Sea and Atlantic Ocean - moderate salinity (~35 g/l) with cooler temperatures.

Highly corrosive environments: 

• Red Sea and Persian Gulf - very high salinity (>40 g/l) and high temperatures.
• Tropical coastal waters - consistently warm temperatures accelerate all corrosion processes.
• Intertidal zones - alternating wet and dry cycles create extreme corrosion conditions.

Corrosion behavior of pump materials

BBA Pumps centrifugal pumps are built from durable, high-quality materials suited for a wide variety of applications. For saltwater applications, several material upgrades are available. Below is an overview of how typical materials perform in seawater conditions.
 
Cast iron
A standard material for many pump casings, cast iron offers excellent mechanical strength and cost-effectiveness. It performs well in freshwater and mild brackish conditions but is not ideal for seawater. Corrosion rates can reach 0.5-1 mm per year depending on temperature and salinity, which limits suitability for long-term use.
 
Chrome Molybdenum
Widely used in BA series pumps for impellers, wear plates and shafts. This alloy provides better corrosion resistance than cast iron. During short-term seawater exposure (days to weeks), corrosion usually remains superficial, but long-term use requires regular inspection.
 
Aluminium
The BA series vacuum system frequently includes an aluminium float tank. Although aluminium naturally forms a protective oxide layer, it is very susceptible to galvanic corrosion when in contact with more noble metals. In seawater, aluminium is therefore not recommended without protective measures.

Stainless steel
BBA Pumps mechanical seals contain stainless steel components, and full stainless steel 316 versions are available as a material upgrade. Stainless steel 316 provides good resistance to seawater corrosion. In the BA series, the float tank can also be supplied in stainless steel for demanding conditions.
 
Bronze
Available as an optional upgrade for the B series self-priming centrifugal pumps. Bronze is traditionally used in marine environments, making it ideal for seawater applications. Its corrosion performance remains stable across varying temperatures and salinity levels.
 
HDPE
HDPE pipework is often chosen for temporary or mobile installations. It is fully corrosion-resistant, making it ideal for seawater projects. However, check the material of quick couplings: galvanized steel couplings are common but may corrode quickly in warm or highly saline conditions.

Conclusion and expert tips

For temporary pumping installations or low-temperature seawater, a standard cast iron BBA pump often performs well. For permanent shipboard systems or long-term offshore deployments, material upgrades are strongly recommended. Warm tropical seawater and high salinity require particular care in material selection.

Tips for successful operation:

• Always verify the local salinity level. Baltic projects differ greatly from tropical sites.
• Match pump materials to temperature and salinity conditions.
• Reduce the combination of seawater and oxygen wherever possible.
• Limit deployment time for standard cast iron pumps. Short projects are generally safe, but long-term use increases corrosion risk.
• Avoid galvanic corrosion between dissimilar metals.
• After use, flush the pump thoroughly with fresh water to remove salt residues.
• Inspect all wet parts regularly for corrosion or pitting.
• Consider protective coatings or cathodic protection for continuous offshore operations.

*Brackish water (a mix of salt and fresh water) contains variable salinity levels, making corrosion behavior difficult to predict precisely.
 
The information shared in this article is based on general pumping experience and does not cover all specific technical details. Therefore, no rights can be derived from the content regarding the use of BBA Pumps equipment for seawater applications. If you are working with a critical pumping installation or have questions about other fluids, please contact our technical team for tailored advice.