Anodised Aluminium Substrate Compatibility for CtCP Coatings
Anodised aluminium substrate for UV CtCP coatings — 1.7–1.8 g/m² coat weight, graining, post-anodic treatment. Orion Freedom Plus and Orion Next specs.
The coating chemistry gets most of the attention in CtCP qualification. The substrate determines whether that chemistry adheres, cures, images, and develops cleanly. Anodised aluminium is the standard base for UV CtCP plates — but not all anodised sheet performs equally with diazo-based lacquers.
This guide covers what plate coaters should verify on anodised aluminium before running DNQ-based CtCP coatings, grounded in Orion's confirmed coat-weight and substrate specifications.
Why anodised aluminium is the CtCP substrate
Offset printing plates require a substrate that is:
- Dimensionally stable under press tension and heat
- Hydrophilic in non-image areas after processing (water-receptive for fountain solution)
- Oleophilic in image areas (ink-receptive where coating remains)
- Flat and uniform for laser imaging at micron-level dot fidelity
Electro-chemically grained and anodised aluminium meets these requirements. The anodic oxide layer provides a porous, hydrophilic surface that bonds with photosensitive coating lacquers. Graining (ball graining or brush graining) creates micro-porosity that improves coating adhesion and water receptivity.
Both conventional and developer-free UV CtCP coatings from Orion target anodised aluminium as the substrate.
Confirmed Orion coating parameters on anodised aluminium
These figures come from Orion's product and technology data. Substrate parameters outside this table are flagged below.
| Parameter | Specification |
|---|---|
| Substrate | Anodised aluminium |
| Dry coat weight | 1.7–1.8 g/m² |
| Graining | Electrically grained (electro-chemically grained) |
| Post-anodic treatment | Required for Orion Next (post-treated aluminium) |
| Sensitivity | 360–375 nm (Orion Next) · 365–405 nm (Freedom Plus) |
| Coating methods | Reverse roll, slot die, flow coating, whirler |
Substrate preparation checklist
Before coating DNQ-based CtCP lacquers, verify:
Graining
- Surface is uniformly grained — no ungrained patches or roller marks
- Graining method matches your coating format (ball-grained for whirler RTU; electro-chemically grained for roll coaters)
- [NEEDS VERIFICATION: Specific Ra (surface roughness) values required per Orion grade — not published in source data]
Anodising
- Anodic oxide layer is uniform across the sheet
- Anodising charge and time are consistent batch to batch
- No bare aluminium exposed through incomplete anodising
Post-anodic treatment (PAT)
Orion's technology page lists post-anodic treatment (PAT) as a variable that affects Orion Next results. Post-treatment modifies the anodic oxide surface chemistry — typically silicate or similar sealing — to optimise hydrophilicity and coating adhesion.
[NEEDS VERIFICATION: Specific PAT chemistry and process parameters recommended by Orion for Freedom Plus and Orion Next — not published in source data. Request method-of-use PDF.]
Cleanliness
- No oil, grease, or handling contamination on surface
- Rinse water quality is clean — residual chemistry from anodising line rinsed off
- Sheets stored in clean, dry conditions before coating
How coat weight affects performance
Orion specifies 1.7–1.8 g/m² dry coat weight for both Freedom Plus and Orion Next on anodised aluminium.
Coat weight is controlled by solution solids concentration, coater speed, and drying conditions. Measure dry coat weight on trial panels before production coating.
[NEEDS VERIFICATION: Orion-recommended solution solids percentage to achieve 1.7–1.8 g/m² per coater type — refer to method-of-use PDF.]
| Coat weight | Typical effect |
|---|---|
| Below 1.7 g/m² | Insufficient photosensitive material; poor dot reproduction; premature plate wear |
| 1.7–1.8 g/m² | Target range — balanced sensitivity, development, and press life |
| Above 1.8 g/m² | Extended self-cure time required; potential development uniformity issues |
Conventional vs developer-free substrate requirements
Both Orion Freedom Plus (conventional positive UV CtCP) and Orion Next (developer-free negative UV CtCP) coat on anodised aluminium at the same target weight. Differences are in the coating chemistry and development step, not the substrate:
If your substrate is qualified for conventional CtCP coating at 1.7–1.8 g/m², it is the correct starting point for developer-free qualification — with PAT and negative-mode imaging added to the evaluation.
| Freedom Plus | Orion Next | |
|---|---|---|
| Substrate | Anodised aluminium | Anodised, post-treated aluminium |
| Coat weight | 1.7–1.8 g/m² | 1.7–1.8 g/m² |
| Graining | Electro-chemically grained | Electrically grained |
| Development | Alkaline developer | Plain tap water |
| Working mode | Positive | Negative |
Qualifying substrate with a new coating supplier
When evaluating Orion CtCP coatings on your aluminium:
- Use your standard production substrate (same graining, anodising, and PAT line)
- Coat at 1.7–1.8 g/m² using the method-of-use parameters for your coater type
- Self-cure minimum 24 hours under yellow safe light
- Image at confirmed UV sensitivity on your plate setter
- Develop per specified chemistry (alkaline or water)
- Evaluate dot reproduction, background, and hydrophilic/oleophilic balance
- Run a short press trial if plate quality passes visual inspection
For the full coating process, see The Complete Guide to UV CtCP Plate Coatings. For developer-free specifics, see Orion Next technology.
Common questions.
What substrate does Orion specify for UV CtCP coatings?
Orion Freedom Plus and Orion Next both target anodised aluminium at 1.7–1.8 g/m² dry coat weight. Orion Next additionally specifies post-treated (post-anodic treated) aluminium.
What coat weight should I target for CtCP plate coatings?
1.7–1.8 g/m² dry coat weight on anodised aluminium. This applies to both conventional (Freedom Plus) and developer-free (Orion Next) UV CtCP coatings from Orion.
Does anodised aluminium differ between conventional and developer-free CtCP?
The base substrate is the same anodised aluminium. Orion Next specifies post-anodic treatment (PAT) as an additional variable. Graining, anodising consistency, and cleanliness requirements apply to both coating paths.
What post-anodic treatment does Orion recommend?
Post-anodic treatment is listed as a variable affecting Orion Next results. [NEEDS VERIFICATION: Specific PAT chemistry and process parameters — request method-of-use PDF from Orion for your substrate line.]