Surface Preparation

Coating integrity and service life will be reduced because of improperly prepared surfaces.  As high as 80% of all coating failures can be directly attributed to inadequate surface preparation that affects coating adhesion.  Selection and implementation of the proper surface preparation ensures coating adhesion to the substrate and prolongs the service life of the coating system.

The majority of paintable surfaces are concrete, ferrous metal, galvanizing and aluminum.  They all require protection to keep them from corroding in aggressive environments.  Selection of the proper method for surface preparation depends on the substrate, the environment, the coatings selected and the expected service life of the coating system.  Economics, surface contamination and the environment will also influence the selection of surface preparation methods.

PREVIOUSLY COATED SURFACES

Maintenance coating will frequently not permit or require compete removal of all old coatings prior to recoating.  However, all surface contamination such as oil, grease, loose paint, mill scale, dirt, foreign matter, rust, mold, mildew, mortar, efflorescence and sealers must be removed to assure sound bonding to the tightly adhering old paint.  Glossy surfaces of old paint films must be clean and dull before recoating.  Washing with an abrasive cleanser will clean and dull in one operation, or wash thoroughly and dull by sanding.  Spot prime any bare areas with an appropriate primer.  Recognize that any surface preparation short of total removal of the old coating may compromise the service life of the system.  Check for compatibility by applying a test patch of the recommended coating system, covering at least 2 – 3 square feet.  Allow to dry one week before testing adhesion per ASTM D3359.  If the coating system is incompatible, complete removal is required.

TOUCH-UP, MAINTENANCE AND REPAIR

For a protective coating system to provide maximum long-term protection, regularly scheduled maintenance is required.  Maintenance includes inspection of painted areas, cleaning of surfaces to remove oils, chemicals and other contaminants, and touch-up of areas where the coatings have been damaged.  Highly corrosive areas, such as those subjected to frequent chemical spillage, corrosive fumes and/or high abrasion or temperature, should be inspected frequently – every six months for example.  Areas exposed to less severe conditions, such as interiors and exteriors of potable water tanks may be inspected annually to assess the condition of the coating system.