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The pre-treatment process must 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 Alphatec projects greater than 500 metres from the coastline, 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 shall be a minimum of 431mg/m2, but advice from pre-treatment suppliers should be taken into consideration.

• For Chrome pre-treatment a Supplier ‘Certificate of Analysis’ should be provided by the customer and attached to Self-Assessment Declaration.
• 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 shall have a recommended conductivity of less than 80 micro Siemens/cm.
• The maximum time between pre-treatment and the application of the powder coating is 24 hours.
• 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 sections must never be handled with bare hands. Clean and lint free cotton gloves must be worn at all times when handling pre-treated sections.

Dry Off Oven (if applicable)

If your site uses a dry off oven to assist in the pre-treatment process, consult your pre-treatment supplier for advice, but generally;

• < 75° C for chrome pre-treatment
• < 120° C for chrome-free pre-treatment
• Applicators must be able to demonstrate compliance with this specification.

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, 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 in accordance with AS 3894.6 methods A&D.
3. Grind all sharp edges with a power tool to a minimum radius of 2mm.
4. Power tool clean welds to AS1627.2 Class 2 to remove roughness. Remove filings, preferably by vacuum or compressed air.
5. Abrasive blast clean all steel surfaces to be painted in accordance with AS1627.4 to visual standard AS1627.9 Class 2.5 (equivalent to ISO8501-1, Sa 2.5: Very Thorough Blast-Cleaning). Use a medium that will generate a surface profile of 35 to 65 microns (as tested to AS3894.5 Method A.) 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 is to be stored in an area which is clean and dry
7. The steel must be coated within 4 hours of blasting.

Application Method

Electrostatic Spray

Cure Schedule for Alphatec

Metal Temperature:
210° : 4 mins minimum
200° : 5 mins minimum
180° : 8 mins minimum

Cure Schedule for Alphatec with RapidCure

Metal Temperature:
200° : 2 mins minimum
180° : 5 mins minimum
160° : 10 mins minimum 

Please note: All RapidCure products can be applied at standard temperatures, but benefits from possible reduction in energy consumption or faster line speeds will be lost.