May 11th, 2024 by . Posted in In Focus, In Focus Industrial, In Focus Marine

Surface preparation shop primed steel

How to prepare shop primed steel surfaces.

A shop primer is designed to protect blasted steel from corrosion between the time of manufacturing and the application of the final anti-corrosive system. Shop primers have limited anti-corrosive properties and form a weak link in high performance anti-corrosive systems.

The best shop primer is NO shop primer!

  Immersion & Splahs zone
  Surface prep.Minimal surface prep.Steel work
ContaminationSalts & chlorides<40-60mg/m²<40-60mg/m² 
Weld SeemsHand WeldingSa 2,5Non-woven abrasive disc (*)P2
Automatic WeldingSa 2,5Non-woven abrasive disc (*)P2
BurnedGas BurningSa 2,5Sanding discP2
Damaged corrodedSpot rustingSa 2,5Sanding disc and/or Non-woven abrasive disc (*)P2
White RustWhite zinc saltSweep blastSanding disc, Non-woven abrasive disc or wire brushp2
Dust ratingISO 8502-311 
  Surface prep.Minimal surface prep. 
ContaminationSalts & chlorides<60-80mg/m²<60-80mg/m² 
Weld SeemsHand WeldingSa 2Non-woven abrasive disc 
Automatic WeldingSa 2Non-woven abrasive disc 
BurnedGas BurningSa 2Sanding disc 
Damaged corrodedSpot rustingSweep blastSanding disc and/or Non-woven abrasive disc (*) 
White RustWhite zinc saltSweep balstSanding disc, Non-woven abrasive disc or wire brush 
Dust ratingISO 8502-311 

Always do an adhesion test when overcoating shop primed steel. The adhesion should be >5Mpa for immersion-, splash zone- and heavy duty atmospheric exposure service and >3MPA for non-heavy duty* atmospheric exposure service.

*Non heavy duty is lower than class C5 according to ISO 12944 and without mechanical load

Steel work is according to ISO 8501-3 standard.

(*) The use of steel wire brush is permitted to remove flash rust out of deep porosities or pittings. Do not polish the surface. The use of supplemental sanding disc or non-woven abrasive disc is permitted at all times.