They are used in various application likes Building exteriors, Appliances, Vents, awnings, dust covers, light fixtures, storm doors, window frames, mailboxes, bathroom accessories, patio covers, and wall switch plates for buildings. Display cases, pans, coolers, and grills for the food industry. Tables, beds, files and storage chests for homes and offices. Golf carts, boats, and camping/fishing equipment for the leisure industry etc.
Details and process of Aluminium Dyes
The procedure consists in producing artificially on the metal surface of porous oxide coating of suitable thickness and bath dyeing of this coating in solution of dyes. Dyestuffs assure level dyeing of the anode coatings and give dyeing with good or very good fastness. The pre-treatment of metal surface consist of common operations, such as:
- Mechanical working
- Degreasing with Solvents or emulsion
- Chemical or electrolytic cleaning
- Brightening of metal surface
- Chemical or electrolytic polishing
- Removing of the unsuitable oxide coat
Setting of the dye bath
Expected results are obtained when dyeing in dye solutions directly after anodic oxidation. The weighted out portion of the dyestuff is pasted with small amount of cold water, diluted with boiling distilled or softened water (condensate may be used, provided it is free from oil or grease). The solution is filtered and diluted in the bath to required volume.
It is recommended to maintain the temperature precisely in the range characteristic of the particular dyestuff, only exceptionally, when the dyestuff is observed too quickly from the bath giving unlevel dyeing, the temperature may be raised above 60 °C. The volume of the is adjusted so as to provide 300-500 ml of dyestuff solutions per 1 sq.dcm of the stained surface. (We recommend to dissolve the dyestuff in de mineralized water.
Tap water is suitable as well but the bath stability can be reduced, however.) The powder dyestuff should be completely dissolved before addition to the bath. It is best to paste it with some of hot water, stirring constantly until a homogeneous paste free from lumps is formed and then to add more hot water with continued stirring so that the paste goes slowly in to the solution.)
| Parameter | Details |
|---|---|
| Aluminium Dye | X gm/litre |
| Sodium Acetate | 8 gm/litre |
| Acetic Acid | 0.4 ml/litre (pH 5.0–5.5) |
| pH of the Dye Bath | |
| Optimum pH | 4.5 – 5.0 |
| Remarks | pH outside 4.0–4.8 reduces bath life due to aluminium accumulation or ageing. Lower pH may cause bronzing. |
| Dyeing Temperature | |
| Optimum Temperature | 55–60°C |
| Remarks | Lower temperatures reduce dye absorption but make stripping easier; however, increase bleeding during sealing. |
| Dyeing Time | |
| Duration | 15–20 minutes |
| Conditions | Continuous agitation at 55–60°C |
| Saturation | Achieved after ~20 minutes; longer time gives minimal intensity increase |
| Standard Dyeing Conditions | |
| Coating Thickness | 12–15 µm |
| Dyeing Temperature | 60°C |
| pH | 4.5 – 5.0 |
| Dye Concentration | 5–10 gm/litre |
| Sealing Process | |
| Purpose | Improves corrosion resistance and wet fastness |
| Sealing in Boiling Water | |
| Temperature | Boiling |
| Time | 45 minutes |
| Medium | Water with 5 gm/litre sealing salt |
| Sealing in Nickel Base | |
| Coloseal | 5 gm/litre |
| pH | 6.0 |
| Temperature | 10 minutes |
| Final Seal | Hot water at pH 5.5 for 5 minutes |
| Anodizing Parameters | |
| Electrolyte Temperature | 18–20°C |
| Current | DC, 1.5 A/sq.dcm |
| Voltage | 14–17 V |
| Anodizing Time | 15–45 minutes |
| Film Thickness | Approx. 20 µm |
