Increases in flow rates reduce the risk of corrosion, and so applications, such as pumps, can be successful uses for 316 types in seawater handling. Stagnant seawater conditions must be avoided. Slow moving water can encourage biofouling, which can then result in shielding or crevice corrosion. Failure to do this has resulted in corrosion to 316 systems. If tubing systems are hydro-tested using seawater, this must be drained and flushed immediately after the test period. Horizontal 316 tube sections handling seawater have been noted to fail by pitting after only short periods.įree draining surfaces and the avoidance of horizontal tube runs are important to the successful use of 316 in contact with seawater. It is important not to let seawater stand in contact with the steel unnecessarily. Water evaporation effects could however increase the corrosion risks in splash zones, if the chlorides concentrate in a damp or wet environment. This may be due to the fact that the steel surfaces are effectively ‘washed’ by the changes in water levels. Intermittent exposure, for example in tidal zones, has been noted as less of a corrosion risk. The levels encountered in even ‘brackish’ waters are above those where crevice corrosion can be expected to be a corrosion hazard. The chloride levels can vary depending on the location and influence of tides. The factors governing the corrosion resistance and hence suitability of the 316 types has been well documented by many workers in these fields of research. Factors governing the corrosion resistance of 316 types in seawater Sulphide inclusions outcropping on the surface of the 303 type are preferential pitting corrosion sites.
#316 stainless steel free#
The 304, and more especially the free machining 303 types, should not be considered suitable for seawater service. This limits the scope for the use of these steels in seawater contact.
They are susceptible to localised attack mechanisms, principally crevice and pitting corrosion. The 316 types are used widely in marine applications, but their corrosion resistance in contact with seawater is limited and they cannot be considered ‘corrosion proof’ under all situations. Selection of 316, 304 and 303 types of stainless steels for seawater applications Introduction
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