NEW HARBOUR TUG

New Zealand Herald, Volume LXXIII, Issue 22318, 16 January 1936, Page 7

NEW HARBOUR TUG

CORROSION MINIMISED STEEL SPECIALLY TREATED DELIVERY HERE SHORTLY In the construction 'of the Auckland Harbour Board's new tug, the William C. Daldy, which is now on its way to New Zealand from Scotland, Epecial precautions were taken to minimise the corrosion of the plates, which is usually very great for a short time after a vessel has been launched. One of the greatest enemies of shipowners is the corrosion of steel plating through its contact with the salt water. In most cases in the mercantile marine the steel plate 3 for vessels are takeu from the mill, rolled to the desired shape, punched, riveted into position, painted and the ships launched. In other words, the mill scale is not removed from the plates. Shortly after the vessels have been placed in the water the action of the salt remoi'es the scale, which takes the paint with it. The stc-el is then fully exposed to the water, with no protective covering. In the past new ships have arrived in New Zealand waters after making their maiden voyage, and on being docked for their first cleaning and painting have been found to be in a very bad state below the waterlino, owing to deep pitting. In one case a new vessel had to have some of its bilge plates replaced a few months after its launching.

To avoid this deterioration the Auckland Harbour Board stipulated in its contract with the builders, Lobnitz and Company, Limited, Renfrew, Glasgow, that the plates of the William C. Daldy below the waterline would have to be " pickled " in acid immediately after they were milled. The " pickling " process consists of placing the plates in a bath of diluted acid to remove mill scale. The jjlates are then hosed with water, after which they are ready for the construction of the vessel. This is a standard Admiralty practice, but one not generally adopted in the case of merchant vessels owing to the extra expense. The additional cost in the case of the William C. Daldy was £IOO. When a vessel has been constructed of " pickled " plates, the paint takes to the steel more readily and is not as easily removed by corrosion. The William C. Daldy is expected at Auckland about the end of next week, and will be placed in the dock as soon as possible for inspection, cleaning and paint--ing. Tho condition of the plates, especially in view of the " pickling," will be carefully examined. Providing the vessel as a whole is satisfactory, it will then be taken over by the board. It is the intention of the board to use the William C. Daldy as the main tug of the port, and to man it with the present crew of the Te Awhina. This vessel, it is believed, will be used to assist th« William C. Daldy in berthing all the large, high-sided vessels that visit the port. It is possible that an engineer and a fireman will be kept permanently on the Te Awhina, and a patent water circulator will be installed to enable steam to be raised quickly. The William C. Daldy will be placed in commission after cleaning, and painting.