sea water pumps discharge manifold- materials and coating

[OMNENG]

Dear Experts,

Our manifold which is used to discharge sea water is having problems since several months. It started having pin holes and leaks at welding joints.

Do you know any technology which repair such manifold easily ? Otherwise, what materials and internal/external coating you recommend if we wish to replace it? I attached drawing of the mentioned manifold.

Below some data:

Location: Oman Gulf
Medium: Sea Water
Temperature: 35
Sodium Hypochlorite Concentration: 0.4 to 0.8 ppm
Flow: up to 60,000 m3/hr
Pressure: 35 m head

Regards

 

[EdStainless]

What is it made from?
Is there any coating inside it now?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[OMNENG]

I thibk it is made of mild/carbon steel and corrocoat internal coating