What Color Coated Aluminum Plate Is
Color coated aluminium plate is a coil-coated flat product: aluminium or aluminium-alloy sheet is cleaned, chemically pre-treated and then painted on a continuous coil line, so the coating is applied and cured under controlled tension before the sheet is cut to length. It belongs to the deep-processing family of aluminium flat products. Because the paint film is applied and cured before the sheet is formed, film thickness, colour and gloss stay uniform over very long lengths, which is difficult to achieve with post-forming spray painting.
Coating Systems Compared
The coating system, not the aluminium substrate, decides how a panel behaves outdoors. The main families are described below.
| System | Resin basis | Dry film thickness | Outdoor performance | Typical use |
|---|---|---|---|---|
| Polyester | polyester, sometimes alkyd modified | 18–25 μm | interior or short-term exterior | interior panels, advertising boards, appliance housings |
| High-durability polyester | silicone-modified polyester | 20–25 μm top coat | medium-term exterior | general exterior cladding, shop fronts |
| PVDF fluorocarbon | at least 70% polyvinylidene fluoride resin | 23–25 μm for two coats, 35–40 μm for three coats | long-term exterior | architectural curtain wall, roofing, landmark facades |
| Epoxy or phenolic lacquer | epoxy or phenolic | 5–15 μm | not intended for exterior | can lids, food-contact packaging |
Polyester gives the widest colour range at the lowest cost and holds gloss well indoors, but its ester linkages are attacked by ultraviolet light and moisture, so heavily exposed facades chalk and fade. Fluorocarbon coatings based on polyvinylidene fluoride resin resist ultraviolet degradation and retain colour and gloss far longer, which is why architectural specifications commonly require at least 70% PVDF resin in the top coat. Exterior architectural coating classes such as AAMA 2604 and AAMA 2605, and the color coated aluminium sheet and strip standard GB/T 22412, are the usual reference points written into a purchase specification.
Substrate and Temper Selection
The substrate is chosen to match the forming severity and the required strength. Grades 1050, 1060 and 1100 are soft, formable and economical and are the common base for interior and advertising work; 3003, 3004 and 3105 add manganese for better strength and stiffness in roofing and cladding; 5052 and 5754 add magnesium and are preferred where coastal or industrial corrosion exposure is severe. Supplied thickness usually ranges from 0.2 mm to 3.0 mm, with coil widths up to about 1600 mm and tempers from O through H14 and H24 to H18 depending on the balance of formability and rigidity required. Pre-treatment is a critical part of the product: a chromate-free conversion coating, or a chromium-based equivalent, is what prevents filiform corrosion from creeping out of cut edges and fixing holes.
Performance Testing and Typical Results
Adhesion: cross-hatch testing per ASTM D3359 and bend testing per ASTM D4145; a 0T to 2T bend without film cracking is a common acceptance limit for architectural panels.
Impact resistance: falling-weight impact per ASTM D2794, typically 20–50 kg·cm without cracking, depending on film build and substrate temper.
Hardness: pencil hardness per ASTM D3363; polyester films normally reach HB to 2H, while fluorocarbon films are slightly softer and more flexible.
Corrosion: neutral salt spray per ASTM B117, where a well-built fluorocarbon system is usually specified at 1000 hours or more, plus humidity resistance per ASTM D2247.
Weathering: colour difference and gloss retention after accelerated exposure, measured with the gloss and colour methods of ASTM D523 and ASTM D2244 and assessed against the chosen coating class.
Applications by Sector
Architecture: roofing and roof panels, curtain wall and cassette panels, interior wall linings, ceilings, honeycomb panels, insulation facing, roller shutter doors and louvres.
Transport: box truck bodies and inner walls, car body panels, railcar interior panels, ship interior linings, traffic signs and advertising display boards.
Appliances: air-conditioner panels, washing machine and refrigerator panels, cabinet fronts and enclosures for digital products.
Printing: PS, CTP and UV-CTP printing plate stock.
Packaging: food cans, can lids, bottle caps, easy-open ends and food boxes, which use food-contact lacquers rather than decorative architectural coatings.
Specification Checklist
State the substrate grade, temper, thickness and tolerance instead of ordering generic color coated aluminium.
State the coating system, the resin content, the number of coats and the dry film thickness of each coat.
State the colour, gloss level, permitted colour difference and the weathering class the facade must satisfy.
State the pre-treatment type and any protective film requirement, because cut-edge corrosion starts at the pre-treatment layer.
State the minimum bend radius the panel will see, so the film can be qualified at that radius before production begins.
Frequently Asked Questions
Q: What is the difference between polyester and PVDF color coated aluminum?
A: Polyester is an economical coating for interior use and short outdoor exposure, while PVDF fluorocarbon contains at least 70% polyvinylidene fluoride resin and keeps its colour and gloss far longer under ultraviolet light.
Q: How thick is the coating on a color coated aluminum plate?
A: Typical dry film thickness is 18–25 μm for polyester, 23–25 μm for a two-coat fluorocarbon system and 35–40 μm for a three-coat architectural system, applied over a thin primer.
Q: Which substrate is best for coastal buildings?
A: A magnesium-bearing grade such as 5052 or 5754 is preferred near the coast, because it resists salt-laden atmospheres better than 1050 or 1100.
Q: Can color coated aluminum plate be bent or profiled after coating?
A: Yes, that is the main advantage of coil coating, provided the film has been qualified for the required bend radius and the tooling does not scratch the surface.
Q: Why does a facade chalk or fade after a few years?
A: Chalking and fading are coating failures rather than substrate failures, and they are usually caused by ultraviolet attack on polyester resin or by an under-built film on a fully exposed elevation.
Q: Is color coated aluminum suitable for food packaging?
A: Food contact requires a dedicated food-grade epoxy or phenolic lacquer rather than a decorative architectural coating, and the finished item must meet the applicable food-contact regulation.
