These Specifications are designed to ensure high-quality of coated products for use in architectural applications.
The surfaces of the parts to be treated shall be clean and free of any oxidation, scale or soils, oil, grease, lubricants, handsweat or any other contamination that may be detrimental to the final finish. The parts shall therefore be etched before conversion coating. Two preliminary pretreatments are defined: standard (compulsory) and enhanced (voluntary, for SEASIDE endorsement).
Chemical conversion coatings
After conversion coating pre-treated aluminium shall not be stored for more than 16 hours. As a rule, they should be coated immediately after pre-treatment. The risk of insufficient adhesion increases the longer the products are stored.
Pre-treated aluminium shall never be stored in an atmosphere that is dusty and detrimental to them. Good atmospheric conditions shall always be maintained in the storage area. All workers handling pre-treated aluminium shall wear clean textile gloves to avoid contamination of the surface.
Anodic pre-treatment (automatic SEASIDE endorsement)
The aluminium surface shall be treated to eliminate all impurities that could pose problems in the anodic pre-treatment. The anodic pre-treatment shall be chosen so as to produce an anodic coating with a thickness of at least 3 µm (not more than 8 µm) without powdering and without surface flaws. The anodic pre-treatment parameters can be as follows:
- Acid concentration (sulphuric acid) : 180-220 g/l
- Aluminium content : 5-15 g/l
- Temperature : 20-30°C (± 1°C of the temperature chosen by the coater)
- Current density : 0.8-2.0 A/dm²
- Agitation of the electrolyte
After anodic pre-treatment, the aluminium shall be rinsed with demineralised water for as long and at such a temperature (less than 60°C) as is required to remove the acid from the pores. The conductivity of the dripping water of the last rinse shall not exceed a maximum of 30 μS/cm at 20°C. The conductivity should only be measured for open sections and not for hollow sections.
Plant installations using this type of anodic pre-treatment shall perform the following additional tests:
Anodising bath:
- the acid concentration and aluminium content shall be analysed every 24 hours of operation
- the temperature shall be checked 1 hour after anodising starts, then every 8 hours.
Testing of the coated finished products:
- Before application, each coating (of a system and/or a manufacturer) shall be tested for resistance to boiling water, followed by an adhesion test (see § 2.4).
- During application, resistance to boiling water should be tested, followed by an adhesion test every 4 hours.
Coating plant installations which decide to use such treatments shall inform their General Licensee, or QUALICOAT if there is not a General Licensee.
Electrophoretic coatings
All products to be coated shall be cleaned by adapted chemical treatment in an alkaline or acid solution. The cleaned surfaces shall be rinsed in demineralised water with a maximum conductivity of 30 μS/cm at 20°C prior to coating. The surfaces should be wettable with water.
The products shall be coated immediately.
All workers handling pre-treated parts shall wear clean textile gloves to avoid contamination of the surface.
Drying
After chemical pretreatment and before the application of organic coating, the products shall be dried thoroughly in an oven. For this purpose, a drying oven shall be installed in each plant.
For continuous treatment the maximum drying temperature allowed is 100°C.
For discontinuous treatment the products shall be dried at the following temperatures:
- chemical chromate conversion (yellow coating): maximum 65°C
- chemical chromate-phosphate conversion (green coating): maximum 85°C
The specified temperatures apply to the temperature of the metallic parts and not to the air temperature. The products shall be dried thoroughly before the coating is applied, irrespective of the production method (continuous/discontinuous).
For anodic pre-treatment, the drying temperature should be less than 80°C to prevent the anodic coating from being sealed.
Alternative chemical pre-treatment systems should be dried following the manufacturer’s specifications.
Coating
For architectural applications the coating plant installation shall use only coatings approved by QUALICOAT. If the approval for an organic coating system is withdrawn,the coating plant installation is allowed to continue using it for a maximum of three months in order to complete unfinished work. However if a colour is banned the coating plant installation shall immediately stop using this colour.
Stoving
The coating line shall have an oven for drying and one for curing; in cases where the oven is combined (performing both functions), an efficient control system for temperature and time shall be in place to ensure that suppliers’ recommended conditions can be followed.
The conditions between the spray booth and the oven shall be absolutely free of dust and contamination.
All organic coatings shall be stoved immediately after application. The oven shall bring the products to the required temperature and maintain them at that temperature for the whole length of the prescribed time.
The temperatures of the products and the stoving times shall match the values recommended in the manufacturer’s technical specifications.
It is recommended to keep the difference in metal temperature during polymerisation phase below 20°C.
It should be possible to measure the temperature over the whole length of the oven.
The oven shall be fitted with an alarm system which operates as soon as the
temperature moves outside the prescribed temperature range.
Laboratory
The coating plant installation shall have laboratory facilities which are separate from the production facilities. The laboratory shall have the apparatus and chemicals necessary for testing and controlling the process solutions and finished products. The laboratory shall at least be equipped with the following apparatus:
1) Specular glossmeter
2) 2 instruments for measuring coating thickness
3) 1 analytical balance (precision 0.1 mg)
4) Cutting tools and instruments necessary for performing the adhesion test
5) Instrument for measuring indentation hardness
6) Apparatus for testing adhesion and elasticity (cupping test)
7) Impact tester
8) Recorder for stoving temperature and time with four different measuring points,
three on the parts and one to measure the air temperature.
9) Conductivity meter
10) Apparatus for testing resistance to cracking on bending
11) Test solution, material and special cutting tool for the Machu test
12) Test solutions for the polymerisation test
13) pH-meter
Each piece of apparatus shall have a data sheet showing the apparatus identification number and calibration checks.
The oven temperature recorder shall be checked and the results shall be registered at least twice per year.
The laboratory conditions may differ from those prescribed by ISO standards for mechanical tests.
