Carbon Steel in Seawater 1

When using carbon steel in seawater without a coating or cathodic protection, it is common to use a corrosion allowance, say 3mm.  However, this is making an assumption about the uniform corrosion rate of steel.  In quiescent seawater it is about 0.1mm/y, rising to ~0.8mm/y at 3m/s flow velocity.

Even at low flow rates, the pitting of carbon steel in seawater is much faster than general corrosion, with typical rates of perforation of 2mm/y at 0.5m/s flow velocity.  This is why carbon steel pipes carrying seawater usually perforate in 18 months to 2 years, depending on flow velocity, unless additional protective measures are used.

Posted on: 7th July 2017

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Image (top left) by Agnieszka