Aluminium cleaning, pre-treatment and anodising are some of the last finishing processes still using highly dangerous chemicals. One materials supplier is trying hard to clean up these areas 

For many decades, hexavalent chrome pretreatment has been the standard for aluminium. More recently, chromebased pre-treatment processes have come under pressure for environmental and health and safety reasons. The first chrome-free pre-treatment processes started to appear in the marketplace about 20 years ago. Today, with almost two decades of operating experience gained, and hundreds of users worldwide, the performance of these programmes is equivalent to the “old” hexavalent chrome products.

Users of chrome-free technology include all the world’s biggest names in the industry. Chemetall’s Gardobond X and OXSILAN AL series - state-of-the-art chrome-free pretreatment processes for aluminium - help producers maximise adhesion and corrosion protection. Both Gardobond X 4707 and OXSILAN AL 0510 hold Qualicoat approvals.

Gardobond X 4707 and OXSILAN AL 0510 feature these qualities: Chrome-free solution for the pre-treatment of aluminium; Spray, dip and cascade application; Easy to handle; Low maintenance process; Easy waste-water treatment; Easy on-line control; Quantitative method for coating weight; Range of industry standard approvals OXSILAN is also a chrome-free multi-metal pre-treatment solution and its approvals include Qualicoat Approval for Powder Paint plus it meets the requirements of AAMA Spec. 2605 for Wet Paint Spray, dip and cascade application.

Optimising anodising
Chemetall has also launched Gardo TP 10748 – an additive for alkaline etching. This new product offers significant improvements for E-6 etching particularly in:

• Rinsing and draining behaviour (i.e. low viscosity in the E-6 bath)
• Homogeneity and matt finish (gloss readings 6 – 8 achievable, 60 ° test)
• Increased productivity (batch optimisation)
• Avoiding of surface defects caused by special alloy composition
• Technical and economical aspects (i.e. less material removal) Furthermore, Chemetall has given a lot of thought to the topic of hot sealing, particularly to minimise the problems occurring in daily operations and thereby to contribute to optimising process safety. These thoughts have led to Chemetall’s new hot-sealing product series: Topseal. It comprises three different processes adapted to the customers’ anodising plants: Topseal Gardo TP 10769: for use in baths without filtration
• Topseal Gardo TP 10779: for use in baths with filtration through a filter pump
• Topseal Gardo TP 10792/Gardo® TP 10793: for use in baths with filtration, optimised to reach longer bath life circles.

When correctly used, products of the Topseal Gardo series achieve weight loss values of 10 – 15 mg/dm². Over the bath service life, this value rises appreciably less than with standard products.

All products can be analysed online or in Chemetall’s laboratory. Chemetall Topseal reliably prevents the formation of sealing smut, gives clean, smut-free surfaces and offers benefits especially on coloured surfaces.

Meeting the challenge of new EC regulation
According to the new European Commission Regulation No 790/2009, all mixtures containing borate must be re-classified as of December 1, 2010 – all products containing 8.5% (and more) of borax must be labelled with the skull and crossbones. Most powder degreasers for anodised aluminium contain borate – and starting December 1, 2010, these formerly harmless cleaning baths will be classified as toxic. Chemetall has the solution: Gardoclean T 5281, a completely borate-free aluminium cleaner.

The product is liquid and thus easy-to-use, it provides good cleaning results also at temperatures below 60 °C (depending on condition of parts) and automatic dosage is possible. Gardoclean has been specifically designed for cleaning aluminium both in the anodising and pre-treatment processes.