Arkema Rilsan Fine Powders T White 1488 AC PA11 is a white-pigmented polyamide 11 powder coating grade supplied for electrostatic spray and fluidised-bed immersion deposition on metallic substrates. The base polyamide 11 is synthesised from 11-aminoundecanoic acid and exhibits a semi-crystalline morphology with a melting peak between 186 °C and 190 °C when determined by differential scanning calorimetry in accordance with ISO 11357-3. The grade designation identifies a specific white colour match and a proprietary additive package that modifies melt coalescence and substrate wetting. Incoming batches should be checked for particle-size distribution by laser diffraction per ISO 8130-13, bulk density per ISO 60, and melt flow rate per ISO 1133-1. The powder is stored below 30 °C at 50% RH or lower to limit moisture pickup; pre-drying at 75–80 °C for 2–4 h is advisable when moisture content exceeds 0.15 wt%.

What Distinguishes T White 1488 AC from Alternative Polyamide 11 and Polyamide 12 Coating Powders?

Relative to unpigmented PA11 fine powders, the white AC formulation incorporates a titanium dioxide-based pigment and a melt-rheology modifier. The pigment raises high-shear melt viscosity and opacity but lowers infrared reflow efficiency, which means infrared oven settings must be recalibrated when switching from natural grades. Compared with PA12 coating powders, PA11 has a higher melting peak, higher flexural modulus, and higher hardness. PA12 has lower equilibrium moisture uptake and better low-temperature impact. The exact additive chemistry of the AC designation is proprietary, and published data for this specific sub-grade is limited; comparative values are therefore taken from public PA11 and PA12 coating-powder literature and should not replace product-specific batch data.

On production-scale corona-charged electrostatic spray lines, the white-pigmented powder is applied at gun voltages of 60–100 kV and transport air pressure of 0.6–1.5 bar. Field experience on conventional metal-coating lines indicates that the high-resistivity titanium dioxide pigment increases the risk of back-ionization at film builds above 350 µm. The defect appears as orange-peel, micro-pinholes, or electrostatic rejection at the surface. Switching to tribo-charging or reducing gun voltage below 38 kV is used to extend the usable film-build window. Film thickness on cured parts is measured by eddy-current instruments according to ISO 2360; corrosion-protective specifications commonly require 120–300 µm, while builds above 900 µm are produced by fluidised-bed immersion rather than cold electrostatic spray. Cold-sprayed powder is fused and cured in a convection oven at 200–220 °C for 10–15 min after the metal surface reaches the cure band; oven set-point alone is not a valid control parameter.

Fluidised-Bed Coating Parameters and Metal Temperature Control

Fluidised-bed immersion with Rilsan T White 1488 AC requires substrate preheating to a metal surface temperature of 250–350 °C before entry into the powder bed. The fluidised bed is maintained at 20–35 °C with a dry air supply having a dew point below −10 °C; immersion times of 2–10 s deposit films from 250 µm to 600 µm. Withdrawal speed and post-dwell draining influence edge coverage and pinhole density. After dip coating, parts are post-cured in a forced-air convection oven at 200–220 °C for 2–5 min once the metal reaches the cure band. Production-scale ovens should be mapped with thermocouple arrays to hold metal surface temperature uniformity within ±10 °C; inadequate preheat causes dry-powder entrapment and poor interlayer adhesion, while preheat above 370 °C yellows the white pigment and embrittles the film. Fluidised-bed lines that process multiple colours require full hopper and bed cleaning to prevent cross-contamination of white batches with darker pigments.

Chemical resistance of PA11-based films is assessed by immersion testing under ISO 2812. Published data for this specific AC grade is limited; general PA11 coating literature shows resistance to aliphatic hydrocarbons, diesel, biodiesel at temperatures up to 60 °C, zinc chloride solutions, and dilute inorganic acids at room temperature. The product is not recommended for continuous immersion in concentrated acetic acid, strong mineral acids, phenolic solvents, or hot benzyl alcohol above 40 °C. Polyamide 11 absorbs polar solvents and is plasticised by moisture; dimensional changes and softening should be expected in humid or aqueous environments. The powder should not be dry-blended with amine-based additives or amine-functional adhesion promoters because these compounds can interact with the polyamide during fusion and cause local crosslinking or colour shift at cure temperatures. Outdoor weathering is evaluated under ISO 4892-2 programme A; PA11 grades generally retain mechanical integrity after 2000 h of accelerated weathering, but the white pigmented surface may show gloss loss and chalking. Long-term UV exposure does not cause catastrophic chain scission because the polyamide 11 backbone has intrinsic resistance, but colour change in white grades is the limiting aesthetic factor.

If Film Build Exceeds 900 µm, How Do Cure Cycles and Edge Coverage Shift?

Thick-film applications above 900 µm shift the limiting variable from electrostatic deposition efficiency to thermal conduction into the substrate. The cure cycle must account for the insulating nature of the deposited polyamide layer; the metal surface may reach the cure band while the outer surface of the film remains below the melting peak. A two-stage thermal profile is used on some fluidised-bed lines: an initial short infrared heating stage of 120–180 s at 220–240 °C to re-melt the outer layer, followed by convection curing at 200–220 °C for 5–10 min. Edge coverage on sharp geometries may be reduced because molten polymer flows away from edges under surface tension; edge radii above 2 mm and pre-treatment of edges improve coverage. For very thick films, cooling must be slow to avoid internal stress and cracking; forced-air quenching is avoided because PA11 crystallises rapidly and can develop shrinkage stresses that reduce adhesion at the interface. Adhesion at thicknesses above 900 µm is evaluated by cross-cut per ISO 2409, pull-off per ISO 4624, and impact per ASTM D2794; the combined results are more informative than visual inspection alone.

Film Integrity Depends on Substrate Preparation, Not Solely on Powder Chemistry.

The salt-spray performance of a PA11 coating is controlled primarily by the substrate pre-treatment and the interface stability. Steel parts are degreased and zinc phosphated; aluminium parts receive chromate conversion or zirconium-based thin-film conversion. On production lines, skipping zinc phosphate on steel reduces ISO 9227 neutral salt-spray resistance by a factor that outweighs batch-to-batch powder variation. Published data for this specific AC grade under ISO 9227 is limited; as a general PA11 coating guideline, a 150–250 µm film on properly phosphated steel is expected to resist scribe creep beyond 2 mm for 1000 h, whereas untreated degreased steel may fail before 500 h. The white pigment does not passivate the substrate; it provides opacity and UV shielding. Parts with sharp edges, weld spatter, or mill scale require mechanical profiling and an additional edge pre-treatment because the powder cannot hide surface defects. The film should be tested for adhesion after cure using cross-cut per ISO 2409 and impact per ASTM D2794 before release to service.

Recovery and re-use of overspray from electrostatic spray booths is limited by the white pigment’s charge retention and particle-size segregation. Cyclone-recovered fines may have a higher proportion of pigment and smaller particle-size distribution than virgin powder; recycling above 30 wt% can reduce flow and alter film appearance. Production lines that reclaim overspray should monitor reconditioned powder using ISO 8130-13 particle-size distribution and ISO 60 bulk density. The powder should not be mixed with other Rilsan colours or with PA12 powders because melt-viscosity differences produce surface defects and reduced interlayer adhesion. Equipment used for PVC or plastisol must be cleaned before polyamide 11 powder is introduced; residual chlorine donors discolour the white film and can generate corrosive by-products during cure.

For regulatory compliance, the product is supplied within the scope of EC 1907/2006 REACH registration for the base polymer and additives. RoHS compliance is assessed against 2011/65/EU Annex II; the white pigment and additives must be confirmed against lead, cadmium, mercury, and hexavalent chromium thresholds. Food-contact status of the base PA11 resin is established under 21 CFR 177.1500 and EU Regulation 10/2011 for specific food categories; the final article must be tested for overall migration and specific migration limits because processing history and substrate residues affect compliance. These anchors are summarised in Table 2. No aerospace or potable-water certification is implied by the product designation; separate approval is required for those end uses.