Hi everyone!
We have a carbon steel heat exchanger TEMA type AES. Cooling water flows through the shell side and the hot 1-butene enters the tube side. The tube-bundle is quite corroded and it has 2 years of service. Attach a picture.

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The heat exchanger is taken out of service on a monthly basis in order to remove polymers on the tube side caused by polybutadiene. The head floating is removed and the water is drained leaving the wet surface and exposed to the atmosphere. The mechanical cleaning tube side takes about 3 days. After this, the heat exchanger is put back on service.

Cooling water flows to <0.3m/s ( <1ft/s) and it is treated with corrosion and scale inhibitors. We assumed that the corrosion is caused by cooling water at low flow velocity and the exposure of the wet tube-bundle to the environment. Can anyone help me how can I mitigate the corrosion?

Thanks in advance.