Nickel alloys and stainless steels for marine and desalination
Seawater is the most common chloride environment there is, and the failures it causes are rarely uniform. They start in a crevice, under a deposit, or where flow velocity drops.
All 13 grades on this page are melted, forged and tested at our own plant in Shanghai and released with EN 10204 3.1 or 3.2 documentation. Chemistry, mechanical results and the heat number travel with the material.
Three mechanisms that decide the grade
Not a materials handbook — just the three things that most often change the answer on a real enquiry.
Crevice corrosion, not general corrosion
Under a gasket, a biofouling deposit or a weld spatter, oxygen stops being replenished and the crevice turns acidic. The alloy that looked adequate in a coupon test fails at the flange face. This is why molybdenum content drives seawater selection.
Velocity has a floor as well as a ceiling
Copper-nickel and the austenitic stainless grades need flow to stay passive; dead legs and intermittent duty are where they pit. Duplex and super-duplex tolerate low velocity differently, which is why piping layout changes the alloy choice.
Chloride stress cracking in hot seawater
The 300-series austenitics are vulnerable to chloride stress-corrosion cracking as temperature rises. Monel 400 and K-500 are the classic answer where that mechanism governs, which is why they appear on pump shafts and valve trim rather than on large plate structures.
13 grades we melt for Marine and desalination
Each one links to its specification page, with chemistry, standards by product form and the EN 10204 documents we issue. Showing 13 of 13.
Monel 400
MONEL 400 exhibits exceptional resistance to corrosion in seawater, brine, and various chemical solutions…
Monel K-500
The alloy achieves tensile strength exceeding 1000 MPa (yield strength ≥ 760 MPa) after heat treatment…
Inconel 625
Inconel 625 exhibits strong resistance to various corrosive media, including seawater, acidic solutions, and alkaline environments.
2507
Far superior to 2205/316L in resistance to chloride stress corrosion cracking, pitting, and crevice corrosion…
2205
Outstanding resistance to chloride stress corrosion cracking (SCC) and pitting/crevice corrosion…
SMO 254
Solid-solution strengthening via alloying elements; only solution annealing needed post-fabrication.
Monel 401
The addition of 0.25% silicon significantly improves chip breakage and reduces tool wear during machining.
Monel 404
The addition of 4.00-7.00% zinc modifies the alloy’s microstructure, preventing hydrogen atoms from diffusing into the metal lattice…
Monel R-405
With a carbon content ≤ 0.05% (significantly lower than MONEL 400’s ≤ 0.30%), MONEL 405 avoids carbide precipitation during welding…
316 / 316L
Outstanding resistance to chloride-containing media (e.g., seawater, brine, chemical solutions with chlorine ions); effectively prev…
321
Outstanding resistance to intergranular corrosion—titanium stabilizes carbon, avoiding chromium carbide precipitation at grain bound…
904L
Excels in resisting corrosion from strong acids (e.g., sulfuric acid, phosphoric acid, acetic acid), chloride-containing media…
XM-19
PREN (Pitting Resistance Equivalent Number) ≥ 42, far exceeding 316L/2205, with excellent resistance to pitting, crevice corrosion…
Three things to put on the enquiry
- Say whether it is immersed, splashed or hot. — Atmospheric marine exposure and 80 °C seawater are different problems. The same grade table does not cover both.
- Name the welding process. — Duplex and super-duplex need a qualified procedure with controlled heat input and proper post-weld cleaning. If the fabrication shop has a procedure, tell us and we will match the delivery condition to it.
- Desalination has two sides. — Brine and permeate sides see different chloride levels and temperatures. Quoting one grade for the whole train over-specifies one end and under-specifies the other.
Marine and desalination: questions buyers ask
The answers below are drawn from the same grade data as the tables above.
Which grades do you supply for marine and desalination?
Monel 400, 401, 404, R-405 and K-500, Inconel 625, 904L, 316 / 316L, 321, 2205, 2507, XM-19 and SMO 254, in bar, plate, strip, seamless tube, forgings and wire.
What is the difference between 2205 and 2507 for seawater?
Both are duplex and both resist chloride stress cracking, but 2507 carries the higher pitting resistance and strength for hotter or more concentrated duty. The comparison note on this site sets the two side by side.
Do you supply pump shaft material?
Monel K-500 bar is the grade most often bought for pump shafts and valve trim in seawater, supplied in the aged condition with hardness reported per heat.
Send the grade, the size, the quantity.
We will quote against your specification, including lead time, inspection level and documents.