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Pre-treatment of Aluminium

Pretreatment Standards

The pre-treatment process must be capable of meeting the performance outputs as described in AS3715 and AAMA-2603

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.

• An etch rate of >1gm/m², is recommended for Duralloy 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.

• Chrome conversion weights must be a minimum of 431mg/m².
• Chrome-free conversion weights – refer to your pre-treatment supplier as currently no standards address chrome-free.
• Chrome-free conversion coatings should be applied and maintained in accordance with the manufacturer’s instructions.
• When changing from chrome to chrome-free your accreditation will require reapplication immediately. Warranty applications through this period will need to be monitored, tested and approved individually.

Final Rinse

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

• Final rinse water run-off from the extrusion shall have conductivity of less than 80 micro Siemens/cm.
• Pre-treated aluminium must be powder coated within the time specified by the pre-treatment supplier – this is generally within 16 to 48 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.

Pre-treatment of Steel

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. Failure to suitably prepare your steel substrate may void your Steel Shield™ warranty.
6. The steel must be coated within 4 hours of blasting and stored in an area which is clean and dry. Dulux Accredited Powder Coaters must comply with the metal pre-treatment guidelines set out in the Accredited Steel Shield™ Manual.

Application

Application Method

Electrostatic Spray

Cure Schedule for Duralloy

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

Project Suitability – Aluminium

Use the tables below to determine the appropriate the product choice you have to gain a Alumi Shield™ warranty by determining the environment that your project will be exposed to. Use this together with the Dulux Macroclimate Corrosivity Corrosivity Zone Maps of New Zealand Guide, available here, the online Dulux SpecMap tool, available here.

Project Suitability – Steel

Use the tables below to determine the appropriate the product choice you have to gain a Steel Shield™ warranty by determining the environment that your project will be exposed to. Use this together with the Dulux Macroclimate Corrosivity Corrosivity Zone Maps of New Zealand Guide, available here, the online Dulux SpecMap tool, available here. Click on the table below for a larger version.

Conditions – Alumi and Steel

Use the following table which references AS 2312.1, SNZ TS 3404 and ISO 9223 to identify the environment, conditions and atmospheric corrosivity categories. To pinpoint your projects corrosivity zone this table should be used together with the Dulux Macroclimate Corrosivity Zone Maps of New Zealand Guide, available here, or Dulux SpecMap tool available here.

Interior and exterior environments close to liquids other than coastal, river and lake salt water environments

Advice Line

Our dedicated consultants can help simplify the specification process, saving you time and money by providing the right coating advice for your project.

Call 0800 800 975

Dulux Alumi Shield™ warranty performance on aluminium:

• 10 Year Durability warranty
• 10 Year Chalk and Colour Fade warranty

On pre-treated architectural aluminium when applied by a Dulux Accredited Powder Coater to the warranty specification on recommended project types and conditions.

For more information on our Dulux Alumi Shield™ warranty program click here.

Dulux Steel Shield™ warranty performance on steel:

• Up to 10 Years Corrosivity warranty
• 10 Year Chalk and Colour Fade warranty

On mild steel, bright/semi bright steel, black steel and blue steel as part of the Steel Shield warranty system when applied by a Dulux Accredited Powder Coater to the warranty specification on recommended project types and conditions.

For more information on our Dulux Steel Shield™ warranty program click here.

Key Limitations for warranties

Environments must be:

• Greater than 100m from the high tide mark.
• Greater than 1m (ie outside the splash zone) for interior environments and greater than 2m on exterior environments that are close to chemically treated liquids (eg near swimming pools, fountains, or showers)
• Greater than 2m (ie outside the splash zone) for interior/exterior warranty in environments that are close to salt water liquids other than coastal, river and salt lake salt water environments (eg near salt water swimming pools)

• Duralloy is NOT suitable in strongly acidic or caustic environments so the pH must be between 5 and 9.

Please note chemically treated water includes antimicrobial treatments, e.g. in pools, anti-corrosive chemicals, and soapy water in bathrooms and showers.

Dulux Accredited Powder Coaters

Only Dulux Accredited Powder Coaters are able to issue our Dulux Alumi Shield™ and Steel Shield™ warranties after demonstrating their capability to meet stringent quality conditions and international standards.

For more information click here.