Goodbye nickel and cobalt
Cold sealing processes based on nickel and if necessary cobalt salts are currently still state of the art and are often used as an alternative to hot sealing processes. Advantages result from shorter sealing times and energy savings. On the waste water side, however, there are disadvantages, as nickel and cobalt have to be removed again. This is where the new development of the HMF - SealAL - process comes in. HMF stands for "heavy - metal - free". The new process is therefore free of heavy metals and otherwise fulfils the properties of a conventional cold seal system. Both colourless and electrolytically coloured surfaces can be sealed. The treatment is completed by an ageing stage in warm water, in which Alfiseal 997 is added. The approval of the process according to Qualanod is in progress.
What advantages does the process offer?
Completely free of heavy metals, low waste water pollution
Application at temperatures below 32 °C
Short sealing times, total sealing time is 1.5 minutes/µm
Applicable on natural and electrolytically coloured surfaces
Good filterability and analysable products
Fulfils the usual sealing test quality demands (weight loss test DIN EN ISO 3210)
The sealing quality is also impressive
HMF - SealAL – process
in practical use
Sealing time
[minutes/µm]
Thickness of the anodic oxide layer
[µm]
Weight loss test results DIN EN ISO 3210 [mg/dm²]
C0
approx. 1 + ageing
15 – 20
approx. 10 - 15
C35
approx. 0.7 + ageing
15 – 20
approx. 15 - 20
Typical application data for the HMF - SealAL – process
Alfiseal 995 / 996
15 - 25 g/l
cold sealing
Alfiseal 997
2 – 4 g/l
ageing stage
Temperature
max. 32°C
cold sealing
min. 60°C
ageing stage
Cold sealing time:
12 – 20 minutes at 15 – 20 µm anodic oxide layer thickness
Ageing:
10 – 18 minutes at 15 – 20 µm anodic oxide layer thickness
Optics of the cold sealed surfaces
Free of smut even on electrolytically black-coloured surfaces (C35)
A good rinsing technology is a prerequisite for sealing that conforms to quality standards.
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