Pretreatment Standards

The pre-treatment process should be capable of meeting the performance outputs as described in AS3715. Compliance to appropriate process parameters is essential in ensuring compliance to etch, conversion coating weights (time/concentration) and conductivity of the final rinse. 

Etch

The etch process is a very important stage of pre-treatment and close consultation with your pre-treatment supplier is strongly recommended to ensure optimum adhesion & corrosion resistance is obtained. As an approximate guide:

• An etch rate of >1gm/m2, is recommended for Copol projects but etch rate advice from pre-treatment suppliers should be taken into consideration.

Conversion Coatings

This is the next pre-treatment process for aluminium to ensure that it is suitably prepared for coating. It is recommended that Chrome conversion weights be a minimum of 431mg/m2, but advice from pre-treatment suppliers should be taken into consideration.

• Non Chrome conversion coatings should be applied and maintained in accordance with the manufacturer’s instructions.

Final Rinse

Final rinse is to ensure optimum surface preparation prior to coating.

• Final rinse water run-off from the extrusion is recommended to have a conductivity of less than 80 micro Siemens/cm.
• The entire area of the aluminium shall be properly pre-treated, appropriate spacing devices should be used.

Handling

Care should be taken with handling to ensure health and safety measures are met and that the substrate is not contaminated.

• Pre-treated aluminium must be handled very carefully with clean lint-free gloves and powder coated within the time specified by the pre-treatment supplier - this is generally within 16 to 48 hours.

Dry Off Oven (if applicable) If your site uses a dry off oven to assist in the pre-treatment process please ensure:

• Post rinse dry off temperature - consult your pre-treatment supplier but generally:
  • < 75° C for chrome pre-treatment,
  • < 120° C for chrome-free pre-treatment.

Steel substrates shall be prepared as follows:

1. Wash and degrease all surfaces to be coated in accordance with AS1627.1 with a free-rinsing, neutral/alkaline detergent, in strict accordance with the manufacturer’s written instructions and all safety warnings.
2. Wash with fresh potable water and ensure that all soluble salts are removed. Testing if required can be done in accordance with AS 3894.6 for the determination of residual contaminants.
3. Grind all sharp edges with a power tool to a minimum radius of 2mm.
4. Hand or power tool clean welds to AS1627.2 to remove roughness. Remove filings, preferably by vacuum.
5. Abrasive blast clean all steel surfaces to be powder coated in accordance with AS 1627.4 to the visual cleanliness standard of SA 2.5. Use a medium that will generate a surface profile of 35 to 65 microns. In situations where it is not possible to prepare your item on all surfaces as described above, for long term protection against corrosion it is strongly recommended whenever possible, that an alternative substrate such as aluminium be considered.
6. The steel must be coated within 4 hours of blasting and stored in an area which is clean and dry.

Application Method

Electrostatic Spray

Cure Schedule

210°C: 8 minutes minimum 

200°C: 10 minutes minimum 

190°C: 15 minutes minimum