BListering of sea water pipeline in OTEC plant

Hi,
I am a mechanical Engineer, working for NAtional Institute of Ocean technology (NIOT, INDIA) WE have a 1 meter diameter sea water pipe line in our experimental Ocean Thermal Energy conversion program. This stee pipe line after two intermittent tests has shown severe blistering to the tune of 4 mm scales coming from the inside of the pipeline. WE have used (6%) NaOcl sodium hypocholorite for preventing biofouling ( separately injected.)

Now what surprises us is that we opened this section of the line before tests and found no scaling and after the tests where the water sea water went thru with NaoCl, and after a week when we opened we found severe scaling..

now is it due to NaoCl??? or was it a long term phenomena which occurred and got accetuanated after this test???
I need some insight in to this??? What is the best solution to prevent this???
Regards

The addition of hypochlorite will significantly increase the oxidizing power (raise the potential) of the a sea water.  That's how it functions as a biocide.  The corrosion will therefore be accelerated by hypo - you can verify this with linear polarization tests with and without the hypo.

You might want to consider polyethylene pipe or omit the biocide for short term pilot work.