3.3.1 The surface preparation by appropriate methods
should be in accordance with the coating manufacturer's specifications
and recommendations. The actual sequence of surface preparation and
coating application depends on the standard selected.
3.3.2 The steel surface should be prepared so
that the coating selected can achieve an even distribution at the
required dry film thickness and have an adequate adhesion by removing
sharp edges, grinding weld beads and removing weld spatter and any
other surface contaminants.
3.3.3 Cleaning to near white metal or equivalent
may be carried out either on incoming materials (plates and profiles),
immediately before the shop-primer application, or after completion
of tanks before the application of the primer coating.
3.3.4 If blast cleaning techniques are to be employed
after completion of tanks, the conditions under which blast cleaning
is carried out should preclude condensation. In this respect, it is
not recommended to carry out blasting when:
-
.1 the relative humidity is above 85%; or
-
.2 the surface temperature of steel is less than
3°C above the dew point; or
-
.3 there is any possibility that the surface of
the steel is wet, or there are traces of moisture, or condensation
occurs before the primer coat is applied.
3.3.5 Blasting abrasives and dust should be completely
removed by means of vacuum cleaning, compressed air and brushes after
blasting operations have finished. The abrasive used for blasting
should be dry and free from dirt, oil, grease, chlorides and suitable
for producing the standard of cleanliness and profile specified by
manufacturer.