METALWORK

Causes
Poor intercoat adhesion, can result from surface contamination, sub-film corrosion and/or inadequate surface preparation prior to painting.
Non-ferrous metals (eg copper, zinc and aluminium) provide surfaces to which paint does not readily adhere unless appropriate surface preparation and priming is carried out.
The cumulative build up of paint coatings will eventually highlight any areas of weakly adhering coatings.

Solution: Remove all loose and defective coatings by scraping and/or the use of a proprietary paint/varnish remover. Remove any surface rust or corrosion salts and feather edges of sound paint with abrasive paper. Wash with hot water and liquid detergent solution to remove all oil/grease and any other contaminants. Rinse thoroughly with clean water and allow to dry. Lightly abrade and spot prime all bare metal with one coat of Macpherson Universal Primer.

Causes
Coating failures/exposure to damp conditions (rusting)
The condition of the surface following preparation is a significant factor in the performance of the paint system. Sub-film corrosion is controlled by thorough surface preparation. An effective rust inhibiting primer together with an appropriate finishing system, applied to achieves optimum total dry film thickness.

Solution: Remove all loose rust and defective coatings by scraping, chipping, wire brushing or abrasion. Feather edges of sound paint with abrasive paper. Remove all dust.
Wash with hot water and liquid detergent solution to remove all oil/grease and any other contaminants, frequently changing the water. Rinse thoroughly with clean water and allow to dry. Spot prime all bare metal with one full coat of a Zinc Phosphate Primer.

Causes
At temperatures above 180°F/82°C, conventional coating systems can rapidly discolour (‘yellow’). At temperatures above 200°F/93°C conventional coating systems are not recommended.

Solution: Domestic hot water systems, radiators and associated pipework etc can be decorated using conventional alkyd systems (>93oC). For superior resistance to ‘yellowing’, Macpherson Acrylic Gloss/Eggshell systems can be used following appropriate surface preparation and priming.

Causes
New, bright condition galvanised (zinc coated) metalwork provides a surface to which paint does not readily adhere. In order to ensure the satisfactory adhesion and long term performance of any subsequently applied paint system, a pre treatment etch primer is recommended.

Solution: Wash with hot water and liquid detergent solution to remove all oil/grease and any other contaminants, frequently changing the water. Rinse thoroughly with clean water to remove all residues. Allow to dry. Pre-treat all areas to be decorated with an application of a suitable Passivating Wash. This pre-treatment will blacken the galvanising and confirm satisfactory surface degreasing. Apply one coat of Macpherson Universal Primer within 48 hours.

Causes
The germination of organic spores contaminating offending surfaces under damp/humid conditions.
These unsightly developments can occur on any surface. It is essential that all infected surfaces are completely sterilised prior to decoration.

Solution: All visible signs of organic growth must be removed by thorough scraping, brushing with a stiff bristle brush (not ferrous wire) and/or washing. The offending areas should then be treated with a liberal application of a Fungicidal Solution, used in accordance with the manufacturer’s instructions.