For pre-painted surfaces, contamination comes essentially from the air and it is
important to have a relevant test to characterize the surface behaviour towards
bacteria according to its conditions of use. A colour test is introduced that enables
to detect active or dead bacteria directly on a contaminated surface. Means to avoid
the proliferation of microorganisms are presented. The behaviour of two pre-painted
topcoats doped with organic and inorganic bactericidal additives is described. On fresh and
clean surfaces, the organic coatings have a very slight biocide effect. The weakest
bacteria are rapidly destroyed whereas the more resistant ones are only inactivated
several days later. On fouled surfaces, the bacterial destruction is very limited.
In the selected experimental conditions, the standard pre-painted topcoat has the same
behaviour as the doped ones.