HIGH QUALITY ANODIZING
Anodizing is an electrochemical process which converts the metal surface into a decorative, durable, corrosion-resistant, wear-resistant oxide layer. This aluminium oxide is not applied to the surface like coating or plating, but is fully integrated with the underlying aluminium substrate. It has a highly ordered, porous structure which allows for secondary processes such as colouring. Our anodizing layers meet all the quality standards for outdoor use, such as QUALANOD and BS.
colour and structure techniques
What is anodizing?
Brushing is done mechanically with a special machine. This machine can brush profiles till 7500 mm length and 300 mm height. Brushing can be used for multiple purposes. For example, it can be used to make small scratches on the aluminium surface to create a stainless steel look. Very light bronze anodizing, combined with brushing creates a colour is named Alu-Inox. It can also be used to make a semi glossy surface by using canvas brushes. The effect is a shiny surface with visible brush marks. Extrusion lines are partly removed. On sheets we recommend to use pre-brushed sheets, for brand names and suppliers please contact our customer service team.
Polishing is done by mechanically with a special machine, using soft cotton buffs to create a shiny glossy surface. This machine can brush profiles till 7500 mm length, 1500 mm wide and 300 mm height. Indoor applications with less thick anodizing layers are shinier and brighter than outdoor applications. Polishing can be combined with colour anodizing to obtain different glossy products. Alumet is also capable in polishing after anodizing, making polished aluminium even glossier, almost varnished appearance. Polishing can be done on profile, flat sheets, or composite sheets, (no folded sheets).
Blasting is done mechanically, by blasting small stainless steel particles on the aluminium surface, creating a smooth matt surface. This machine can blast profiles till 7500 mm length, 1500 mm wide and 300 mm height.
Blasting can be combined with etching or chemical brightening, making the appearance sparkle glossy. Blasting can be done on profiles, sheets or folded sheets. For sheets we need of 3 mm thickness. This thickness is to prevent deformation during the blasting process.
Cleaning is the first step of the chemical pre-treatment of aluminium products. It takes about 10 minutes in special soap to clean the product from dirt and oil.
After rinsing the product is ready for etching or anodizing, depending on the desired finish. The alkaline rinse water is neutralized with the acid rinses after anodizing.
Matt etching is the second process step in chemical pre-treatment of aluminium products. It takes between 12 minutes to etch the product in soda, to gives the product a silky smooth appearance. Combined with blasting, the chemical etch needs shorter process times.
If polished, the etching process is skipped. The alkaline waste water is neutralized with the acid rinses after anodizing. Alumet has a filter press to retrieve the dissolved aluminium, so the filter cake can be used in other industries.
Chemical brightening is an alternative for matt etching. Instead of making the product more matt, the brightening step adds more gloss to the product. It also gives the colour a “bright” reflection.
Chemical brightening is done in acid, making the surface shiny by removing alloy particles from the surface. The acid wastewater is neutralized by mixing it with the alkaline wastewater.
Anodizing is an electrochemical process which converts the metal surface into a decorative, durable, corrosion-resistant, wear-resistant oxide layer. This aluminium oxide is not applied to the surface like coating or plating, but is fully integrated with the underlying aluminium substrate. This means it cannot chip or peel. It has a highly ordered, porous structure which allows secondary processes such as colouring. Anodizing process is done by electrolysis of water, splitting water (H20) molecule into Oxygen (O) and Hydrogen (H). The oxygen will react with the aluminium product to form aluminium oxide (AlO2). Our anodizing layers meet all the quality standards for outdoor use, such as QUALANOD and BS.
Colouring is the most important step after anodizing, Alumet anodises aluminium in colour and gloss. We do not use pigments, but metal salts to obtain the colours. These metal salts will reflect and bend light, creating “colour”. Therefore all electrolytic colours are highly UV resistant. This means no fading! Most metal salts are deposited by electrolytic processes, using tin for brown – bronze and cupper for reddish colours. Gold is made by absorption, using iron salts. The gold colour will lighten up a bit in the first month, because of a chemical reaction between iron, aluminium, water and UV. This reaction only accurs in the first month, than this process stops and is extremely UV resistant. All colours are lightfast and will remain sparkling for a long time.
Sealing prevents corrosion
The final step in anodizing is sealing. We need to close the pores that were created during anodizing. If the pores are closed the product has its anti-corrosion properties, as pollution and oxygen cannot reach the aluminium below. We use hot boiling water to seal the anodizing layer. The aluminium oxide molecules change from tetrahedral to octahedral in the process, expanding and closing the pores.