AISI 304 vs AISI 904L: Choosing the Right Stainless Steel to Maximise Submersible Electropump Lifespan

In the world of submersible electropumps, austenitic stainless steel is the industry standard: robust, reliable, and stable across various hydraulic conditions. However, when moving from "standard" wells to environments with high salinity, mineralisation, or elevated temperatures, the choice between AISI 304 and AISI 904L is no longer just a detail—it is a strategic variable that directly impacts the electropump lifespan and the Total Cost of Ownership (TCO).

When Accelerated Corrosion of Electropumps Occurs

Chlorides exceeding 500 ppm, aggressive salts, and temperatures above 20°C accelerate localised corrosion in submersible electropumps. In coastal wells, saline irrigation, desalination plants, and thermal mines, this leads to:

• Operational lifespan reduced by 50–70%.
• Replacements as often as every 24 months for electropumps in AISI 304.
• Additional costs for extraction, system downtime, and energy.

Chemical Composition: Nickel and Molybdenum as a Shield

Both AISI 304 and AISI 904L start with a base of 18% Chromium. However, the composition of AISI 904L drastically increases resistance to chlorides:

The result is a significantly more stable protective barrier, especially in wells with chlorides >300 ppm, where AISI 304 begins to show signs of corrosion within the first few years.

Estimated Electropump Lifespan and TCO: When 904L Costs Less than 304

In neutral water, AISI 304 remains the most cost-effective choice. Under standard working conditions, an AISI 304 electropump lasts an average of 10 to 15 years, ensuring reliability and a highly competitive overall cost.

The situation changes as water becomes more aggressive. In these conditions, AISI 904L maintains a similar lifespan but offers a decisive advantage: thanks to its superior chloride resistance, it reduces costs by avoiding premature replacements and repeated maintenance.

The most significant leap is seen in critical applications, such as mining or thermal waters. Here, AISI 304 has a very limited operational life, while 904L ensures much higher durability. This increased longevity translates into an 80% reduction in maintenance costs and a significantly longer overall system life.

FB Pompe Solutions: The Right Steel for Every Well

When water is neutral (chlorides below 300 ppm), AISI 304 is simply the most efficient choice.

However, when the well becomes challenging (brackish water, salt pans, thermal mines), you need a material engineered to endure. This is where AISI 904L comes in—investment-cast and optimized for the most corrosive environments. Our FBSX Series in AISI 904L steel harnesses this full potential: it triples the Mean Time Between Failures (MTBF), reduces maintenance by 80%, and allows for the recovery of the +40% initial investment in approximately 18 months.

In certain waters, choosing the right steel means avoiding problems before they even start.