Online spray pretreatment is designed best on conveyor speeds article geometry. It is generally used in conveyorised plants where article types are few, geometry is similar and quantities are large.

Articles move over the conveyor through modular spray tunnel where the chemicals are sprayed. The chemical tanks with pumps are placed below or on the side of the tunnel. Due to continuous spray the interaction between article surface and chemical is very fast.

For elevated tempertature zones insulated tunnel tank modules are provided.