ECOLOGICAL PREPAINT TREATMENT OF ALUMINIUM ... - Aluplanet

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ODIP bonding mechanism Organic Dry In Place Chemical bond to metal oxide Chemical bond with powder coat Excellent paint adhesion O- O- O- R- R- R- Cleaned Aluminium Organic D I P Coated Aluminium Powder Coating DIP-O- DIP-O- DIP-O- DIP- DIP- DIP- R-DIP-O- R-DIP-O- R-DIP-O- Painted Aluminium Slide 8: ODIP bonding mechanism Chromium-free Passivate The most versatile replacement for phosphating and chromating prior to painting, are the new Chromium-free Passivates (CFP) which are suitable for all alloy types and readily applied by spray or immersion. Completely free of chromium and phosphates, they are generally based on group four transition metals such as Zirconium or Titanium. Coatings display a mineral like grain structure which means they do not exhibit ‘mud cracking’ and are more heat resistant. Film colour is blue to iridescent, dependant upon the material being processed. Surface characteristics are shown on slide 9, contrasted against chromate. Surface characteristics CHROMATE PASSIVATE Slide 9: characteristics of chromate against passivate CFP has the benefit of being able to function on mixed metal lines processing metals such as aluminium, steel and zinc thereby giving the applicator greater flexibility. Studies have shown that passivate performance is independent of solution operating temperature when used over steel and galvanised substrates, therefore it allows the applicator to benefit from room temperature operation. For aluminium and magnesium, whilst room temperature operation
produces more than acceptable results and the highest levels of performance are achieved when the solution is operated at elevated temperature around fifty centigrade. CFP technology meets latest European Union legislation, ensuring applicators and end users are fully compliant. It is an ideal replacement for phosphates and chromates when excellent paint adhesion with superior corrosion resistance is required. It has been shown to exhibit superior mechanical properties such as paint adhesion, whilst giving excellent corrosion resistance. They are highly suitable to meet a wide variety of industrial performance standards. As a ‘stand alone’ passivate film, they also show good levels of corrosion protection for everything except high copper alloys such as wrought 2000 series. The current commercially used offerings fail to consistently meet the 168h neutral salt spray level as defined by MIL- DTL-5541F. There are new areas of research which show improved ‘stand alone’ performance of CFP over aluminium and it has been speculated that the minimum requirement of the standard may be achieved for high copper alloys. CFP performance. Evaluation studies have demonstrated that the performance of the final coating is essentially not dependant upon the application method of the passivate. Results shown on slide 10 are of comparative tests confirming that same performance is achieved whether CFP application is by immersion or spray. Additional validation work has been completed to determine the influence of substrate type. Slide 11 highlights the results of corrosion testing using neutral salt spray, after 700h exposure for Al 6061 wrought alloy, Galvanized sheet and Cold rolled steel. The results confirm the suitability of the technology for multi metal application, which is important for process flexibility. CFP spray vs immersion CFP substrate variation Neutral salt spray 2184 hour exposure Polyester Powder Coat nominal 50 microns thickness Neutral salt spray - 700 hour exposure Type Spray Immersion Alloy Al 6061 Al 6061 Paint type Epoxy powde r coat Paint thickness Nominal 50 microns Creep back mm 0 0 Aluminum 6061 (Spray) - ASTM D1654 (Rating 10) Aluminum 6061 (Immersion) - ASTM D1654 (Rating 10) Rating ASTM 1654 10 10 Aluminum 6061 ASTM D1654 Rating 10 Galvanized G90 ASTM D1654 Rating 9 Cold Rolled Steel ASTM D1654 Rating 10 Slide 10: application method Slide 11: substrate type To be commercially viable as a prepaint treatment for aluminium, it is also necessary to establish that CFP provides comparative performance with different aluminium alloy types. The results on slide 12 show adhesion and corrosion tests for three common alloys, all were treated through the same prepaint sequence and then coated with a polyester powder coat. After 4000 hours neutral salt spray exposure, extruded alloys Al2024, 5052 and 6061 show no signs of corrosion and no loss of paint adhesion.
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ECOLOGICAL PREPAINT TREATMENT OF ALUMINIUM ... - Aluplanet

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