Once the surface to be painted is completely clean, it should first be
painted using anticorrosive paint, preferably a "zincromat"-type base
coat, applied both inside and outside the spiral and suction tube. After
the base coat has been applied, putty should be used to cover any parts
requiring this in order to obtain an improved finish. Once the putty has
dried it should be sanded down first with a course-grain abrasive
followed by a fine grain and lastly a water abrasive. Before the finishing
paintwork is applied, which could be with vinyl paint or any other type of
paint for metal, the structure should again be cleaned with rags and
thinner in order to remove any dirt and possible grease which may have
built up during handling. Finally, the finishing paintwork is applied with
the required uniformity. A spray gun should ideally be used, in which
case this should first be inspected to ensure the nozzle is completely
free of obstructions and paint residue. (Fig. 14)
Figure 14: Finished axial turbine
2.2 Manufacture of the suction tube
The suction tube is manufactured using the same materials as the spiral,
and also the same equipment and tools.