Is the exterior of waterproof casing painted or not?

The outside of the waterproof casing is painted for aesthetic purposes, while the inside is painted to prevent rusting.
Waterproof casing is definitely painted inside, generally depends on the needs of the customer to decide whether to paint the exterior, because if painted, waterproof casing cast in concrete and concrete bonding is not good, so sometimes customers request not to spray paint, the benefits of not spraying the exterior is to allow waterproof casing better bonding with the concrete, the interior should be painted rust-proof paint, but now the manufacturer from the aesthetic point of view on the inside and outside are painted of.
If the waterproof casing arrives at the site to install pre-buried outside wall do not do paint treatment, if you arrive at the site and wait a while to start installing pre-buried, in order to prevent rust on the outside wall need to do paint treatment.
If it is a large diameter air conditioning cooling water pipe and installed in the well without waterproof requirements of the pipe, you can directly use the tin casing. However, if the design requires the use of steel casing, then the steel casing is used, but the cost is higher.
When welding is used, the welding needs to be completed at the same time, the bottom of the pipe needs to be subarc welded, the pipe should not be burned back and forth when welding, and X-ray inspection should be done after welding to prevent the damage caused by welding to the pipe.