The document describes an acid cleaning system developed by Coil Coating Technologies BV to clean and pretreat metal surfaces without producing wastewater. The system reduces industrial water consumption by more than 95% and eliminates wastewater discharges. It uses a mild acidic cleaner at a pH of around 4.0 for steel and multi-metal lines or a stronger acidic cleaner at a pH of around 2.0 for dedicated aluminum lines. The system achieves effective cleaning through a closed-loop process where rinse water is recycled back into the cleaner bath.
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Cleaning & Pretreating without the production of waste water a gentle way of preserving freshwater resources
1. 1
Cleaning & Pretreating without the
production of waste water
a gentle way of preserving freshwater resources
Environmental sound pretreatment system asEnvironmental sound pretreatment system as
developed bydeveloped by
Coil Coating Technologies BVCoil Coating Technologies BV
Barry GroeneveldBarry Groeneveld
2. 2
Cleaning & Pretreating without the
production of waste water.
• Clean water is essential
for life as we know
• 71% of earth surface is
covered with water
• only 0.6% is available
as freshwater
• Agriculture is using
70% of the freshwater
resources
• Presence of clean, potable water will be scarce
• Existing sources should be protected well
• Industrial processes should be minimised in water consumption
• Effluents should be clean, but better not produce any effluents at all
FACTSFACTS
3. 3
Cleaning & Pretreating without the
production of waste water.
• they require very thorough rinsing, because
• alkaline residues are detrimental for paint adhesion
• initially excessive attack on aluminium → smut and fast build-up
of aluminium in bath solution
• tendency to form scale deposits at equipment, heating spirals,
pipes, nozzles, etc.
• regular dumps of bath needed (or even continuous overflow)
• maintenance
Alkaline cleaners are the industrial standard,
however:
4. 4
Cleaning & Pretreating without the
production of waste water.
• Especially developed by CCT for the Coil Coating Industry
• Driving forces: waste reduction; environmental protection
• Reduction of industrial water consumption with more then 95%
• NO WASTE WATER dumps
• Highly effective surfactants secure a good quality cleaning
• 30 years of practical experience
Acid Cleaning System (ACS)
5. 5
Cleaning & Pretreating without the
production of waste water.
• Water based process, no VOCs
• Liquid chemicals only → easy bath maintenance and adjustments
• Easy process automation
• Intermediate bath temperature; low energy consumption
• Very long bath life span
• Low chemicals consumption
Acid Cleaning System (ACS)
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Cleaning & Pretreating without the
production of waste water.
• Water refreshment of final rinse is regulated by evaporation losses of
cleaning and rinsing baths. Conductivity final rinse is kept below 20 µS/cm
• Preferably double set of squeegee rolls after each bath
• Rinse water is counter cascaded to Cleaner bath (back-flow)
• Composition of ACS chemical bath is compatible with conversion coating
• No drain !
Acid Cleaning System (ACS)
THE PRINCIPLESTHE PRINCIPLES
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Cleaning & Pretreating without the
production of waste water.
• All baths are made up and replenished with DI water
• Requires Stainless Steel equipment
• Equilibrium drag-out back-flow will be reached
• Cleaner bath kept in good shape by continuous oil removal (oil separator)
• Acidic solution preferentially dissolves Al-oxides and metallic impurities,
without etching the Aluminium substrate
• In practice Aluminium content in cleaner bath remains < 2.0 grams/liter
Acid Cleaning System (ACS)
8. 8
Cleaning & Pretreating without the
production of waste water.
• Mild acidic cleaner for steel and multi-metal lines (pH ~ 4.0)
• Strong acidic cleaner for dedicated aluminium lines (pH ~ 2.0)
• Initially fluoride-free. Complex fluorides may be added separately if
additional etching is required (“dirty substrate”)
Acid Cleaning System (ACS)
TWO FLAVOURSTWO FLAVOURS
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Cleaning & Pretreating without the
production of waste water.
• Often etching of aluminium is advised to remove metallic impurities in
outer surface layer of the aluminium substrate
• CCT has developed thick conversion coatings, with layer weight up to
1000 mg/m2 that incorporate the metallic impurities
• These coatings contain complex fluorides, which etch the surface before
the actual conversion coating is formed
• As a result, the negative influence of alloying elements on the corrosion
resistance is greatly neutralised
• Application by chemcoater process → dried-in-place, no-rinse, no-waste
• Adhesion properties comparable or better than conventional chromate +
organic paint primer
What about corrosion resistance?
10. 10
Cleaning & Pretreating without the
production of waste water.
For a cleaner environment…
without compromising cleaning quality…
and with lower applied costs per sqm.
This lecture is not about conversion coatings. Since already a few decades most of you make use of no-rinse conversion coatings, which are applied by chemcoater and dried in-place.
This is all about the cleaning stage. Since the very beginning of our industry, when Joseph Hunter developed his first machines in the ’30s of the previous century, cleaning already took place with ”water & soap”, the so-called alkaline cleaners. Ever since alkaline cleaner are the industrial standard, however:
