Why Gulf seawater is different
Compared with open ocean water, the Arabian Gulf is warmer, saltier and busier with marine life. Salinity regularly goes above 40,000 ppm and summer water temperatures pass 35 °C. Heat speeds up pitting and crevice corrosion in stainless steel, and slow-moving water lets deposits settle and attack the metal underneath.
The usual candidates
- Titanium. Practically immune to seawater at normal cooling temperatures. It costs more up front, but over the life of the unit it is usually the cheapest option.
- Copper-nickel (90/10, 70/30). Naturally resists marine growth and has a long track record. It does not like high velocity, sand or polluted water with sulphides.
- Super duplex (2507) and 6Mo (254 SMO). Strong and good value for shells and piping, but crevice corrosion becomes a risk above roughly 30 to 40 °C, so respect the temperature limits.
- Standard stainless steel (316L). We don't recommend it for Gulf seawater. Chloride pitting usually shows up quickly.
A simple rule
For shell and tube units on seawater, titanium tubes with a clad or coated tubesheet give the best reliability. Cu-Ni is worth considering where temperatures are moderate and the water is clean and flowing at a controlled speed.
Our rule of thumb: if the unit is hard to reach, or a leak would stop production, go with titanium.
Don't forget the details
Gaskets, tubesheets, velocity limits, galvanic couples and cathodic protection all affect how long an exchanger lasts. A good material in a poor design will still fail early.
If you send us your process data, we'll suggest the most economical material for your conditions and explain why.