Hello Rainer,
Glad to hear from you again. Just some information I have on the type of coating that was applied to the hulls of the Type IXC's boats.

The paint below the water line was as follows: The base coat was two coats of white lead b1.11 or two coats of lead free rust inhibiting R.S. 13. The finish coats were one boot topping gray W.L. 23a and one W.L. III 23b.

The paint above the water line including fittings on deck, but where galvanized Z priming coats are omitted is as follows: Base coats was the same as below the water line. Finish coats were 2 camouflage, oil resistant, type 58, 58-1 or 58-2.

The above was per specifications coming from surrander documentions. It goes on to say that the exterior paint departs from that given in the specifications in that all black paint is used on all vessels of the type which were seen at Portsmouth at the time.

It also goes on to say that the underbody paint used does not notably inhibit marine growth. Each vessel which was dry dock at Portsmouth has been foul underwater and had required extensive cleaning.

Scott

It does not say how long the boats sat in the water without moving before being dry docked. Most of the paint I deal with in the past for submarines are made to brake off with the marine growth as the boat goes through the water, thus keeping the hull free of marine growth. The boats I have seen that set in water for any length of time before we dry docked them had developed marine growth.