Author: Ian Craig | Date: 08/07/15 Issue 3 | Reference: R50059/575
General
This specification only refers to the refinishing of Plastisol cladding with PPG Selemix Paints. Other substrates such as polyester powder coat are covered in document R50059/574
Substrate Preparation
Galvanised Steel coated in PVC Plastisol
Areas of mould or algal growth should first be treated with a proprietary fungicide (used according to the manufacturer’s instructions). This should be done (and repeated if necessary), prior to washing down the surface to be painted.
It is recommended that the surface is thoroughly pressure washed using a suitable detergent to remove dirt, oil, grease and all other contamination. The surface should be rinsed well with clean water and allowed to dry.
1. New Plastisol
This should be abraded with P320-500 abrasive discs or Red Scotchbrite and degreased with a solvent-based degreaser either by spraying on and wiping off with a clean rag, or by wiping on with a clean rag and wiping off with another clean rag.
The surface can then be painted directly with Selemix Direct Topcoat 7-53X. Any small areas of loose or flaking Plastisol coating should removed by scraping off to the bare metal. Prepare and prime these areas prior to painting as below in Section 4.
2. Aged, Sound Plastisol
If the substrate has been exposed to outdoor conditions for less than 5 years old, treat as new. If older, the substrate should be pressure-washed clean, rinsed well, and allowed to dry thoroughly prior to painting directly with Selemix Direct Topcoat 7-53X.
Any corroded areas (usually along edges, overlaps, or mechanically damaged areas), should be cleaned to bright metal substrate by abrasion, feathering back to sound Plastosyl. Any small areas of loose or flaking Plastisol coating should removed by abrasion, feathering back to sound Plastosyl.
Areas of bare metal resulting from any operations described, should be prepared and primed prior to painting as described in Section 4.
3. Unsound Plastisol
If the Plastisol is peeling or flaking, or poorly adhering (i.e. likely to fail a crosshatch test), it should be stripped down to the galvanised steel substrate beneath. This can be carried out in several ways as appropriate:
3.1. Chemical Stripping Use a proprietary chemical stripper as per the manufacturer’s instructions. Apply, allow to react, and remove the Plastisol by scraping. Repeat if necessary.
After stripping, the surface should be pressure washed with detergent to remove all residues, rinsed with clean water and allowed to dry. The surface should then be prepared and primed prior to painting as described in Section 4.
3.2 Blast Cleaning Blast clean to SA2.5. All coating should be removed completely. Remove all blast debris. The surface should then be painted as soon as possible to avoid corrosion. Prime in PPG Delfleet Etch Primer (either F393 or F379) and recoat with Selemix Direct Topcoat (minimum 80 microns DFT above the blast profile).
3.3 High Pressure Water Blasting Wet blast to remove all unsound Plastisol. Take care that the pressure is not so high as to damage or distort the panels. The resulting bare metal area should be prepared and primed as described in Section 4 prior to coating with Selemix Direct Topcoat 7-53X
4. Bare Metal Areas
These areas should be abraded with P180-240 abrasive discs, (taking care to remove any traces of old coatings, contamination, corrosion and white zinc salts), and degreased with a solvent based degreaser.
The substrate should then be primed in PPG Delfleet Etch Primer (either F393 or F379). Two coats should be applied as per instructions on the relevant technical data sheet. The primer should be dried for at least 30 minutes prior to recoating. If blast cleaned, a high build primer (Selemix 2.705.0500 PU Primer), should be applied over the etch primer to give extra build to cover the blast profile by at least 50 microns. Selemix Direct Topcoat 7-53X should then be applied.
5. Old Paintwork
If areas have been, or are suspected to have been previously refinished, the paintwork should be checked to ensure that it is sound and does not delaminate. Unsound paintwork (that would not pass a crosshatch adhesion test), must be stripped, either chemically or by blast cleaning as described in Section 3.
Sound old paintwork should be abraded with P320-500 abrasive discs or Red Scotchbrite and degreased with a solvent-based degreaser either by spraying on and wiping off with a clean rag, or by wiping on with a clean rag and wiping off with another clean rag. Selemix Direct Topcoat 7-53X can be applied directly to the paintwork. It is recommended that a small test area is painted first to check if there is any reaction to the new coating being applied.
Painting of Topcoat
Selemix Direct 7-53X Direct Topcoat is activated 4:1:1 with 9-070 Hardener and 1-480 Thinner. 1-208 Slow Thinner or 1-470 Very Slow Thinner can also be used depending on weather conditions. Apply in 2-3 coats by conventional, HVLP, or airless spray to give 80 microns dry film thickness.
Application of Paint Systems
All paint systems must be applied according to the respective Technical Data Sheets F379 / F393 Etch primers may require an induction period prior to application. Please refer to TDS. F379 / F393 Etch Primers must be applied to a dry film thickness of 15-25 microns 2.705.0500 PU Primer must be applied to a minimum film thickness of 50 microns over a blasted profile. 7-53X Selemix Direct must be applied to a minimum dry film thickness of 80 microns.
Painting should not be carried out at temperatures below 5C, or if the temperature is likely to drop below 5°C during the drying time of the paint Painting should not be carried out if the Relative Humidity is above 80%
The dew point should be tested prior to painting. The substrate temperature should be at least 3°C above the dew point to avoid condensation forming.
Temperature, Relative Humidity and Dew Point should all be recorded at the time of painting.
PPG Warranty Issue
Any warranty can only be issued if discussed and agreed with PPG prior to the start of any work. The relevant warranty can be issued only after the following. This must be agreed between the applicator and technical representative from PPG.
- Agreement on Method Statement for substrate preparation and paint application before start of work.
- Site visit from PPG representative (before start of work). Observe existing condition of item/s to be painted. They will advise on substrate preparation if required.
- Adherence to both applicators method statement and PPG guidance on substrate preparation. Follow this document. Paint application as referred to on relevant Product Data Sheets for the PPG products.
- Final inspection of completed job from PPG representative in presence of applicator to sign off job completion.
These should be considered as the absolute minimum levels of activity prior to issue of the relevant warranty. Promain.co.uk
