Match grade to dry film thickness, surface treatment to resin and application method. For epoxy: C-28E (> 500 μm DFT) or C-90E (200–500 μm). For vinyl-ester: C-28V (thick lining) or C-90V (mid-DFT). For airless-spray < 200 μm: C-150E. For pigment or cosmetic use: arsenic-free C-400N.
Glass flake is only as effective as its geometry allows — and geometry must match the coating you are building. The four variables that decide your grade are resin system, dry film thickness (DFT), Chemical Resistance requirement, and target MVT (moisture vapour transmission). The sections below walk through each application class; the table in the final section collapses all recommendations into a single matrix.
How do I match glass flakes to epoxy anti-corrosive coatings?
For epoxy systems always use the E variant — silane-treated with KH-550 to couple the glass surface to the epoxy matrix. E-treatment prevents filler pull-out during cure, maintains Chemical Resistance over the service life, and is the baseline for any reactive epoxy formulation.
Which grade suits heavy-duty epoxy flooring and thick-film linings?
Use C-28E / RCF-600 for environments that demand maximum barrier — industrial flooring, heavy-duty concrete-reinforcement coatings, sealants, and thick-film protective systems. The 300–1700 μm platelet length produces the highest aspect ratio and the longest tortuous diffusion path, which is the dominant MVT-reduction mechanism at DFT above 500 μm. Below that film thickness, C-28 cannot lay flat, and a smaller grade outperforms it.
Which grade suits mid-DFT epoxy primers and sealers?
For DFT in the 200–500 μm range, step down to C-90E / RCF-160T. Its smaller D50 (≈ 160 μm) lies flat in a thinner film, giving a smoother surface than C-28 while still delivering barrier overlap. Typical uses: marine epoxy primers, bridge-deck sealers, and concrete-repair coatings where a balance between build and surface finish matters more than absolute maximum barrier.
How should I match glass flakes to vinyl-ester systems?
Vinyl-ester coatings demand the V surface treatment (KH-560 silane), which couples glass to the vinyl-ester resin and preserves Chemical Resistance in aggressive acid and oxidising service — FRP tanks, chemical-process piping, flue-gas desulphurisation (FGD), and power-plant linings.
Which grade suits FGD and thick-film tank linings (DFT 500 μm – 2 mm)?
C-28V / RCF-600 is the default for thick vinyl-ester linings applied by roller or brush. The high aspect ratio maximises barrier-path extension in films from 500 μm up to 2 mm, and the silane coupling holds up under continuous hot-acid immersion. Typical specifications: FGD absorber tower linings, power-plant scrubber internals, chemical-processing storage tanks.
Which grade suits medium-DFT vinyl-ester coatings (DFT 200–500 μm)?
C-90V / RCF-160 delivers flatter, more uniform barrier layers in mid-thickness films without the surface irregularity coarser flakes can produce. Good fit: smaller chemical-process vessels, splash zones in FRP equipment, and manway or flange linings where surface smoothness aids cleaning.
Which glass flake works for airless-spray coatings under 200 μm DFT?
Thin-film protective coatings — applied by airless spray on steel and concrete exposed to aggressive chemicals, on internal linings of naval, railway, and road tanks, and on chemical, petrochemical, biofuel, and derivative storage tanks — need a fine flake that lies flat and passes through spray tips. Specify C-150E for DFT < 200 μm; use C-400N (D50 ≈ 15 μm) for gloss topcoats or very thin primers. Both grades retain usable Chemical Resistance for splash-and-spill service; for continuous immersion at this DFT, re-evaluate and increase the film thickness with a coarser grade.
Which glass flake is best as a pigment substrate or extender?
Glass flake as a pigment substrate or extender carries pigment powder, increases volume, improves hiding power, and delivers metallic/pearlescent optical effects with excellent weather resistance. Specify C-150N or C-400N / RCF-015. The flat, smooth platelet surface is the substrate on which pigments are deposited or aligned; thickness of 2–3 μm and tight PSD give consistent sparkle and orientation in automotive, decorative, and industrial effect coatings.
Which glass flake is safe for cosmetic applications?
Because cosmetic pigments contact skin, only arsenic-free grades are acceptable. Specify C-400N with arsenic content < 10 ppm — D50 ≈ 15 μm, thickness 2–3 μm. This grade is the standard substrate for pearlescent cosmetic pigments, nail and body products, and any skin-contact decorative finish. Do not substitute untested industrial C-glass grades: trace arsenic from standard melts can exceed cosmetic-grade thresholds.
What is the complete selection matrix?
The table below consolidates the recommendations above. Match your resin system and target DFT to find the specified grade and silane coupling agent.
| Resin System | Application | Dry Film Thickness | Recommended Grade | Silane |
|---|---|---|---|---|
| Epoxy | Heavy-duty flooring, thick-film tank lining | > 500 μm | C-28E | KH-550 |
| Epoxy | Mid-DFT marine primer, concrete sealer | 200–500 μm | C-90E | KH-550 |
| Vinyl-ester | FGD absorber, power-plant lining, FRP tank | 500 μm – 2 mm | C-28V | KH-560 |
| Vinyl-ester | Chemical-process tank, medium-DFT lining | 200–500 μm | C-90V | KH-560 |
| Epoxy (spray) | Pipeline & railcar anti-corrosive primer | < 200 μm | C-150E | KH-550 |
| Any thin-film | Gloss topcoat, industrial airless-spray primer | < 150 μm | C-400N | None |
| Pigment | Effect pigment substrate, decorative extender | n/a | C-150N / C-400N | None |
| Cosmetic | Skin-contact pigment (arsenic-free mandatory) | n/a | C-400N (As < 10 ppm) | None |
Typical dry film thickness for general protective coatings — used to line naval, railway, road tanks, and petrochemical, biofuel, and derivative storage vessels — is less than 200 μm and is applied by airless spray using C-150E or C-400N.
Frequently Asked Questions
Which glass flake grade gives the highest Chemical Resistance?+
C-28 delivers the highest Chemical Resistance in immersion and aggressive-chemical service. The coarse 300–1700 μm platelets, at a 5 ± 2 μm nominal thickness, reach an aspect ratio up to 560:1 — producing the longest tortuous diffusion path through the cured film. Combined with a vinyl-ester matrix (C-28V, KH-560 silane) for acid tanks and FGD linings, or epoxy (C-28E, KH-550 silane) for marine and immersion coatings, C-28 is specified when dry film thickness is ≥ 500 μm. For thinner films where C-28 cannot lay flat, step down to C-90V or C-90E, which still exceed E-glass extenders on both Chemical Resistance and MVT.
How does glass flake particle size affect MVT (moisture vapour transmission)?+
Larger, higher-aspect-ratio platelets reduce MVT more than fine flakes — at equal loading. Each flake forces water vapour to detour around it, so longer platelets multiply the effective film thickness by up to 10×. C-28 achieves the lowest MVT when DFT allows (> 500 μm). C-90 is the best compromise at 200–500 μm DFT. C-150 and C-400 are optimised for DFT < 200 μm, where coarse flakes would protrude or leave voids. Rule of thumb: choose the largest grade that still lies flat within your DFT, because aspect ratio — not loading wt% — dominates MVT performance.
When should I specify surface-treated V or E grades instead of untreated N?+
Specify V or E whenever glass flakes are incorporated into a reactive thermoset — V (KH-560 silane) for vinyl-ester, E (KH-550 silane) for epoxy. The silane coupling agent chemically bonds the glass surface to the polymer, preventing filler pull-out, reducing film microcracking during cure, and sustaining Chemical Resistance over the service life. Use untreated N grades only for inert matrices (polyester FRP lay-ups, mortars, certain pigment extender blends) or where the formulator adds their own compatibiliser. Using N where V/E is required typically cuts useful field life from 25 years to under 10.
Which glass flake is recommended for airless-spray anti-corrosive coatings with DFT under 200 μm?+
Use C-150E or C-400N for airless-spray coatings targeting DFT < 200 μm. At this film thickness, only fine flakes lie flat without clogging spray tips or leaving surface defects. C-150E (epoxy-silane treated, D50 ≈ 100 μm) is the default for thin-film anti-corrosive primers on tank exteriors, pipelines, railcars, and biofuel storage. C-400N (D50 ≈ 15 μm) goes thinner still and is the standard for gloss topcoats and high-finish metallic primers. Both retain usable Chemical Resistance for splash-and-spill duty; for continuous immersion at < 200 μm DFT, re-evaluate the system — C-28 or C-90 at higher DFT usually delivers longer service life.
Is glass flake safe for cosmetic and skin-contact pigment applications?+
Yes — but only arsenic-free C-400N is suitable for cosmetic and skin-contact use. Specify C-400N with arsenic content < 10 ppm; its 15 μm average diameter and 2–3 μm thickness give a smooth, light-reflective platelet ideal for pigment substrates, pearlescent effects, and extender duty. Never substitute untested industrial grades in cosmetic formulations — trace arsenic from standard C-glass can exceed cosmetic-grade limits. For non-skin-contact decorative paints, automotive metallics, and industrial effect pigments where exposure is indirect, C-150N or C-400N both work; cosmetic, nail, and body products must use the verified low-arsenic C-400N only.
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