316L stainless steel probes are standard for marine platform gas turbines, but salt spray environments accelerate corrosion—proper passivation treatment is key to maintaining their performance and longevity.Gas Pressure Scanwelcome to click on the website to learn more!
Passivation removes free iron from the probe surface, forming a protective chromium oxide layer that resists chloride attack. The process involves immersing the probe in a 20-30% nitric acid solution at 40-60°C for 30-60 minutes, followed by thorough rinsing to remove acid residues. A marine test showed that passivated 316L probes had a corrosion rate of 0.005mm/year in salt spray, compared to 0.03mm/year for unpassivated ones.
Post-passivation, avoiding mechanical damage to the oxide layer is critical. Even minor scratches (e.g., from improper handling) can expose bare steel, creating corrosion sites. Using plastic-coated tools during installation and storage in dry, dust-free conditions preserves the layer. In a shipboard application, a scratched probe showed pitting after 3 months, while an undamaged one remained corrosion-free for 12 months.
For high-salinity areas (e.g., coastal desalination plants), enhancing passivation with a 0.5% sodium dichromate additive in the nitric acid bath increases layer thickness by 20%, further reducing corrosion. This modified process extended probe life by 50% in a Gulf of Mexico offshore test.
Regular re-passivation (every 6-12 months) is recommended, especially after cleaning or maintenance that may compromise the oxide layer. This proactive step ensures 316L probes continue to perform reliably in the harsh, salt-rich environments of marine gas turbines.