Arcdip AU 240 Thin-Film Pretreatment Compatible Cathodic Electrocoat
Arcdip AU 240 is a cathodic electrocoat formulated to deposit and adhere over thin-film zirconium oxide conversion coatings, and to behave consistently when steel, zinc-coated steel and aluminium pass through the tank in the same load. It carries the adhesion that a zinc phosphate crystal structure would otherwise provide.
Grade Arcdip AU 240 | Range Electrocoat | Technology Waterborne cathodic electrocoat, acid-solubilised, formulated for zirconium thin-film pretreatment
Technical Data Sheet
Arcdip AU 240
Issue 2026.09
1. Product description
A cathodic electrocoat formulated to deposit and adhere over thin-film zirconium oxide conversion coatings rather than over a conventional zinc phosphate layer, and to behave consistently when steel, zinc-coated steel and aluminium pass through the tank in the same load. Thin-film pretreatment lowers sludge, drops the pretreatment operating temperature and removes the phosphate rinse load, but it leaves a much thinner and smoother conversion layer, so the electrocoat has to carry adhesion that a phosphate crystal structure would otherwise provide. Specified when a line is converting its pretreatment, or when a mixed-metal load makes a single phosphate chemistry impractical.
2. Features
- Adheres over thin-film zirconium oxide conversion coatings
- Consistent deposition on steel, zinc-coated steel and aluminium in one load
- Suited to lines converting from zinc phosphate to thin-film pretreatment
- Result governed by pretreatment coating weight and rinse conductivity
3. Recommended uses
Cathodic electrocoat for lines converting their pretreatment to zirconium thin-film, and for mixed-metal assemblies carried on one jig where a single phosphate chemistry is impractical.
Substrates. Zirconium pretreated cold rolled steel, hot dip and electrogalvanised steel, aluminium sheet, extrusion and castings, and mixed-metal assemblies carried on one jig.
4. Typical properties
| Property | Typical value | Method |
|---|---|---|
| Technology | Waterborne cathodic electrocoat, acid-solubilised, formulated for zirconium thin-film pretreatment | Formulation |
| Supply form | Feed components for a cathodic electrocoat bath | Visual inspection |
| Bath non-volatile content | 18 to 22 per cent by weight | ISO 3251 |
| Bath pH | 5.5 to 6.3 | ISO 19396-1 |
| Bath conductivity | 1200 to 1900 µS/cm, referred to 25 °C | Calibrated conductivity cell, technique as in ISO 7888 for water, no coating specific standard method |
| Dry film thickness, open surface | 18 to 25 µm, standard build | ISO 2178 on uncoated steel, ISO 2360 on aluminium; on zinc-coated steel the magnetic reading includes the zinc layer, so the film is measured by difference against the same part before coating, or by eddy current to ISO 2360 where the zinc layer is thick enough for the probe |
| Cross-cut adhesion | Classification 0 to 1 on each metal in the load, 1 mm cut spacing | ISO 2409 |
| Neutral salt spray, scribed panel over zirconium pretreatment | Duration and scribe creep limit agreed for each substrate and conversion coating weight; a comparative laboratory result, not a prediction of service life | ISO 9227 exposure, assessment to ISO 4628-8; on aluminium in the load, filiform resistance to ISO 4623-2 where agreed |
| Resistance to condensation humidity | Duration and blistering rating agreed for each substrate in the load | ISO 6270-2 exposure, blistering assessed to ISO 4628-2 |
| Cure confirmation | Passes the solvent rub count agreed for the line after the stated bake | ASTM D5402, with oven profile by attached thermocouple |
Typical values, not a specification. Values for each batch are given on its Certificate of Analysis.
5. Application
| Parameter | Guidance |
|---|---|
| Method | Cathodic electrodeposition by immersion in a circulating bath, with the part as cathode and anolyte cells removing the acid released at the counter electrode so bath pH stays in control |
| Surface preparation | Cleaning and a zirconium oxide thin-film conversion coating, with coating weight and final rinse conductivity controlled on the pretreatment stages, not in the electrocoat tank |
| Bath make-up and replenishment | Feeds added to the circulating bath with demineralised water as bath analysis requires |
| Bath temperature and deposition | 28 to 32 °C; 150 to 250 V DC applied over 120 to 180 s, below the rupture voltage of the bath |
| Rinse | Ultrafiltrate rinse followed by a demineralised water rinse, with dragout returned to the tank |
| Cure schedule | 175 to 190 °C metal temperature for 20 min at temperature, confirmed by attached thermocouple oven profile |
| Next step or overcoat | Liquid or powder topcoat where required, with intercoat adhesion confirmed on the combined system to ISO 2409 |
Process. Immersion in a circulating cathodic bath at 28 °C to 32 °C, 150 V to 250 V DC applied over 120 s to 180 s, ultrafiltrate and demineralised water rinses, then bake at 175 °C to 190 °C metal temperature for 20 min at temperature. Pretreatment coating weight and rinse conductivity are the two variables that decide the result and both are controlled on the pretreatment stages, not in the e-coat tank.
6. Storage and handling
Store the feed components in closed original containers in a cool, dry place, protected from frost and direct sunlight; the operating bath is kept circulating and is not left standing. Shelf life is stated on the label and Certificate of Analysis. Handle and use the product in line with its Safety Data Sheet.
7. Safety and regulatory information
Read the Safety Data Sheet before use. Safety Data Sheets and regulatory declarations are issued by our technical centre against the product and batch supplied, so they are sent on request rather than published. Request a Safety Data Sheet or declaration.
This Technical Data Sheet is published for on-screen reference. The information is given in good faith from laboratory and application experience and describes typical values; it is not a specification and does not replace a trial on your own substrate and line. Arctic Materials may revise this sheet without notice. Issue 2026.09.
Technical Data Sheets on this site are for on-screen viewing. For a controlled copy, write to tech@arcticmaterials.com.
Other grades in this range
Need a Safety Data Sheet, a regulatory declaration or a grade specified to your line? Contact our technical centre.