Pipeline identification colour coatings are protective topcoats whose colour is itself the safety information: they must block water, oxygen, chloride and industrial gases from the steel substrate and, at the same time, present a hue that a plant operator or emergency responder can recognise from several metres away. In China that hue set has been governed since 1 March 2026 by the mandatory standard GB 2894-2025 “Colours for safety signs and safety information”, which merges the former GB 7231-2003 (pipeline identification colours), GB 2893-2008 (safety colours) and GB 2894-2008 (safety signs). For a coatings supplier the practical consequence is not a new palette but a new obligation: faded or discoloured safety colour is now an explicit reason to repair or replace a sign, so colour retention becomes a compliance property, not a cosmetic one.
TL;DR
- Timeline. GB 2894-2025 was issued 30 May 2025 and became effective 1 March 2026, replacing three standards at once; 37 new pictograms were added, 34 modified and 1 deleted. The eight pipeline identification colours were carried over.
- Hard dimensions. Colour bands are 150 mm wide; the spacing between two adjacent markings must not be less than 10 m; a hazard band for dangerous-chemical lines is 150 mm yellow with 25 mm black edges on both sides.
- Failure mechanism. Photons at 290–400 nm drive photo-oxidation of the binder; epoxy and aromatic-isocyanate polyurethanes absorb strongly and yellow first. Natural exposure in Wanning (Hainan) gave about 94 % gloss loss, chalking grade 4 and colour-change grade 3 after 36 months for an alkyd-ester primer plus outdoor polyurethane topcoat.
- Pigments are the weak link of colour accuracy. Bright green, scarlet and medium yellow have historically leaned on azo pigments or lead chromate; long-term outdoor work should move to mixed metal oxide (MMO) pigments, quoted at lightfastness grade 7–8 on the blue-wool scale.
- System choice. Work back from ISO 12944-1/-9 durability — L < 7 years, M 7–15, H 15–25, VH > 25 to first major maintenance: alkyd or waterborne for indoor pipe racks, aliphatic polyurethane for typical outdoor plant, polysiloxane or FEVE fluoropolymer for C4–C5 long-cycle work.
- Application control. Blast to Sa 2½, keep the substrate at least 3 °C above dew point, stay below 85 % RH, and split colour bands either wet-on-wet or after abrasion of an cured film — painting beyond the maximum recoat interval is where intercoat failures start.
Key numbers at a glance
- 3 → 1: GB 2894-2025 supersedes GB 2893-2008, GB 2894-2008 and GB 7231-2003; issued 2025-05-30, effective 2026-03-01.
- 8 identification colours: water — bright green (G03); steam — scarlet (R03); air — light grey (B03); gas — medium yellow (Y07); acid or alkali — violet (P02); flammable liquid — brown (YR05); other liquids — black; oxygen — light blue (PB06). Codes follow GB/T 3181 (standard colours of paint films).
- 150 mm / 25 mm / 10 m: band width, black edge width of the hazard band, minimum distance between markings.
- Every 6 months: the new standard requires safety signs to be inspected at least twice a year, with seven listed conditions (fading, deformation, cracking, peeling, damage, occlusion, blending with the surroundings, insufficient lighting) triggering repair or replacement.
- 94 % vs 59.5 %: gloss loss after natural exposure at Wanning — 36 months for an alkyd-ester/polyurethane system, 24 months for a fluoropolymer topcoat (93 % for an acrylic polyurethane in the same 2-year comparison).
- 0.51 W/(m²·nm) at 340 nm: typical xenon-arc setting under ISO 4892-2 / GB/T 1865, with black-panel temperature 65 ± 3 °C, 65 ± 5 % RH and a 102 min light / 18 min spray cycle.
- 30 % gloss loss: the practical threshold for “significant ageing” in GB/T 1766 grading (0–5 scale, 0 = no change), measured per GB/T 9754 / ISO 2813 at 60°.
- 35 μm per coat: typical dry film for one coat of a high-performance topcoat (about 100 μm wet, ~220 g/m² per coat); total build is set by the ISO 12944-5 system table and the project specification.
- 420 g/L: above this VOC content in the ready-to-spray state a 4 % consumption tax applies in China; GB 30981-2020 capped solvent-borne architectural/structural topcoats at 500 g/L and waterborne at 300 g/L.
- 5400–5800 MJ/m² per year: tropical solar radiation (Hainan) given in the annex of GB/T 9276 with rainfall above 1500 mm — the same topcoat can differ several-fold in service life between sites.
1. What the revision actually changes for coatings
1.1 From three documents to one
A piping-marking package used to be checked against three texts at different levels of abstraction: medium colours in GB 7231-2003, safety and contrast colours in GB 2893-2008, sign design and placement in GB 2894-2008. The mismatch showed up commercially as “colour approved against an old sealed sample, pictogram bought to the new edition”. GB 2894-2025 collapses the three into one document and adds requirements for colour specification, board materials, placement and maintenance. As explained in a March 2026 public communication from the Guiyang emergency-management authority, the standard does not apply to traffic signs used in rail, road, inland waterway, maritime or air transport.
1.2 Three consequences for the coating supply
First, acceptance now references one text, so traceability of the colour standard and the sealed sample sits more squarely with the coatings supplier. Second, “discolouration or fading” is a replacement trigger, which turns colour retention into a contractual performance item alongside adhesion and film thickness. Third, a six-monthly inspection rhythm guarantees that partial repair and overcoating will happen in service; compatibility and surface preparation must therefore be specified at design stage, not discovered at year two.
2. The eight identification colours and the pigments behind them
| Medium class | Identification colour | Code (GB/T 3181) | Common pigment route | Main long-term outdoor risk |
|---|---|---|---|---|
| Water | Bright green | G03 | Phthalocyanine blue + azo yellow shade; chrome green; cobalt green (MMO) | The yellow component fades first, hue shifts towards blue-green |
| Steam | Scarlet | R03 | Toluidine/naphthol reds; quinacridone or DPP high-performance reds; iron oxide reds | Low-cost organic reds lose chroma within 1–2 seasons and start to chalk |
| Air | Light grey | B03 | Titanium dioxide + carbon black + iron yellow | Hue is stable; failure shows as gloss loss, chalking and dirt pick-up |
| Gas | Medium yellow | Y07 | Lead chromate (restricted); benzidine yellows; antimony-titanium / titanium-chromium / bismuth yellow | Lead route squeezed by heavy-metal limits; organic yellows fade outdoors |
| Acid or alkali | Violet | P02 | Dioxazine violet; cheaper organic violets | Weak violets fade and reduce contrast with the yellow/black hazard band |
| Flammable liquid | Brown | YR05 | Iron oxide brown; iron-chromium brown (MMO) | Pigments are robust; risk concentrates in binder yellowing and insufficient film |
| Other liquids | Black | — | Carbon black | Strong heat absorption; higher skin temperature accelerates thermal ageing |
| Oxygen | Light blue | PB06 | Ultramarine; phthalocyanine blue + titanium white | Ultramarine is acid-sensitive; shade drifts green as the binder yellows |
Mixed metal oxide pigments are formed by high-temperature solid-state reaction above 1000 °C into a stable lattice; public data typically quote blue-wool lightfastness 7–8, D50 of 0.3–1.0 μm and a wide pH tolerance, which makes them the safer route for permanently exposed marking. For dark lines, IR-reflective grades of the same family reduce surface heat build-up. Upgrading the pigment package does not by itself deliver colour accuracy: batch ΔE still has to be managed by tinting discipline and a sealed reference panel.
3. Why the colour fails before the corrosion protection does
3.1 Binder: bond energy decides who breaks
UV photons in the 290–400 nm band carry enough energy to cleave common polymer bonds; radical chain photo-oxidation then manifests as chalking. Aromatic epoxies and aromatic-isocyanate polyurethanes absorb strongly in that band, while acrylic, FEVE fluoropolymer and polysiloxane binders (Si–O backbone, roughly 443–460 kJ/mol) resist it. On site this is why the worst-looking pipe run is often not the sunniest one but the one painted with an aromatic hardener.
3.2 Pigment: shade drift comes with the binder
Once the matrix chalking exposes pigment to direct radiation, its own degradation rate jumps. In mixed shades (bright green, light grey, light blue), fading of a single component changes hue long before overall colour intensity looks tired — which is precisely what the “discolouration/fading” replacement clause detects.
3.3 Judgement: turning “it looks tired” into a measurement
Three numbers do the job: 60° gloss retention (GB/T 9754 / ISO 2813), colour difference ΔEab measured with a spectrophotometer under D65 (GB/T 3979, GB/T 11186), and the 0–5 ratings of GB/T 1766 for gloss loss, colour change, chalking, cracking, blistering and rusting. For identification colour specifically, the compliance-relevant question is whether the chromaticity coordinates still sit inside the permitted range of the standard — which is why reference panels and instrument records must be archived from day one.
4. Topcoat systems compared
| Topcoat (ISO 12944-1 code) | Outdoor colour retention, typical | Reported accelerated weathering | Recoating ease | Relative cost | Fit for identification colour |
|---|---|---|---|---|---|
| Alkyd (AK) | ~2–4 years to marked gloss loss | Product standards sit in the hundreds to ~1000 h range | Easy, compatible with itself | Low | Indoor racks, light duty, temporary marking |
| Aliphatic acrylic polyurethane (PUR) | ~5–10 years | 1500–2500 h xenon (public data) | Good with cleaning and keying | Medium | Workhorse for general outdoor plant and tank exteriors |
| Acrylic polysiloxane (PS) | ~10–20 years | 3000–4000 h, ≥80 % gloss retention for light shades | Moderate; surface cleanliness matters | Medium-high | C4–C5 long-cycle compromise between life and price |
| FEVE fluoropolymer (FEVE) | ~15–25 years and above | 3000–5000 h with low gloss loss and small ΔE (manufacturer data) | Hard: low surface energy needs abrasion or a tie coat | High | Where hue must hold and access is difficult |
| Waterborne / solvent-free epoxy with waterborne topcoat | System dependent, usually below fluoropolymer | By product standard and specification | Easy | Medium | VOC-driven conversions, confined-space work |
These ranges come from public test data and project experience, not from standard clauses, and accelerated hours cannot be linearly converted into outdoor years. Comparative studies report correlation coefficients below 0.8 between 3000 h xenon exposure and 12–15 months of natural exposure at humid-tropical (Qionghai) or dry-hot (Dunhuang) sites, and even negative correlation at acid-rain or cold sites. Use accelerated testing to rank formulations; use natural exposure to set maintenance intervals.
5. System design and film build
| Setting | Corrosivity / durability target | Representative system (DFT) | How the identification colour is produced |
|---|---|---|---|
| Indoor pipe rack, plant rooms | C2–C3, L–M | Anti-corrosive primer 40–60 μm + intermediate 60–80 μm + 2 × 30–35 μm topcoat ≈ 160–210 μm | Topcoat is the base colour; bands applied locally |
| Outdoor units, tank farms, acid industrial atmosphere | C4, H | Epoxy zinc primer 60–80 μm + epoxy MIO 2 × 80 μm + polysiloxane or FEVE 2 × 35–40 μm ≈ 250–280 μm | Two-coat colour; stripe coat at welds and supports |
| Coastal and offshore | C5–CX, H–VH | Inorganic zinc 75 μm + epoxy glass-flake 150 μm + 2 × 30 μm topcoat ≈ 285 μm (published example) | Weathered topcoat plus scheduled colour audit |
Three cautions. Zinc-rich primers and micaceous intermediate coats buy corrosion life, the topcoat buys colour and weatherability; spending the whole budget at the bottom and fitting a cheap topcoat gives the familiar result “the protection is fine, the marking has failed”. Black and dark lines run noticeably hotter than light ones, so thermal cycling and insulation design should be considered together. Low-surface-energy topcoats that have weathered for years will not take an overcoat reliably unless abraded or tie-coated.
6. Application window and colour-band splitting
6.1 Three preconditions
Blast carbon steel to Sa 2½ (ISO 8501-1 / GB 8923) with profile matched to the system; keep the substrate at least 3 °C above dew point; stop above 85 % relative humidity. Dew-point control is the item most often skipped on marking jobs: morning condensation on a cold pipe wall shows up six months later as blistering at the edge of a colour band.
6.2 Intercoat window
Two-component topcoats carry both a minimum and a maximum recoat interval — the first avoids solvent entrapment and blistering, the second reflects the closing of the mechanical keying window. Taking a common published range of 6–24 h at 23 °C, anything applied after the maximum interval requires abrasion first. Colour bands can then be masked wet-on-wet (crisp edge, continuous intercoat) or painted over a cured film with a template, in which case overlap must be controlled and adhesion at the boundary sampled.
6.3 Edges, welds and valves
Welds, free edges, bolt ends and flange faces are the preferred channels for medium ingress and deserve stripe coating before the main pass. Marking must cover line starts, ends, crossings, bends, valves and both sides of wall penetrations — exactly the geometry where film thickness is hardest to hold. Record measured film thickness together with marking locations, so that a later colour touch-up cannot quietly push the system beyond its designed build.
7. Colour QC and the six-monthly inspection
7.1 Delivery and commissioning
Four checks at delivery: compare against the sealed panel under D65 and log ΔEab (ΔE ≤ 3 is a common field tolerance, while tinting plants quote batch control around 1.5); repeat under illuminant A to catch metamerism; verify wet or dry film to confirm hiding; and confirm 60° gloss, because the same formulation at a different gloss reads as a different colour.
7.2 In service
Inspect at least every six months and repair or replace on any of the seven listed conditions. The first three map onto coating ageing grades under GB/T 1766; the rest are layout, lighting or information problems that repainting cannot solve. Where light levels are low, the standard requires retro-reflective or self-luminous materials, which can be combined with phosphorescent coating systems for evacuation routes.
8. Frequently asked questions
Q1. Existing plant is still marked to the old standard — is that an immediate breach?
The three previous standards were withdrawn on 1 March 2026, so requirements are now read from GB 2894-2025. The defensible route is an audit register — prioritise dangerous-chemical lines, confined spaces and fire service piping, log colour codes, locations and inspection dates, and keep the remediation plan and interim signage on file rather than waiting until the whole plant is repainted.
Q2. Can we just brush a coat of matching colour over the old film?
Restoring the colour is not the same as restoring compliance. If the existing film is chalked or has lost adhesion, a new coat only delays the failure and hides evidence. Check adhesion by cross-cut or pull-off (GB/T 9286 / GB/T 5210), remove chalk, key the surface, verify compatibility — fluoropolymer and polysiloxane films in particular need abrasion or a tie coat.
Q3. Why do scarlet and medium yellow always fade first?
Those hues have traditionally relied on lower-lightfastness azo pigments or on lead chromate. The former photo-degrade; the latter is being pushed out by heavy-metal limits and procurement compliance. Quinacridone/DPP reds and MMO yellows hold much longer at a higher unit price, which is recovered through longer recoating intervals.
Q4. Does 3000 hours of xenon equal how many years outdoors?
There is no universal factor. Correlation between accelerated and natural exposure depends strongly on the site climate, with published coefficients below 0.8 in some comparisons. Rank formulations with accelerated testing; derive maintenance intervals from natural exposure data for comparable systems and climates.
Q5. Is a fluoropolymer topcoat worth it on an indoor pipe rack?
Usually not. In C2–C3 interiors the governing damage is cleaning, abrasion and impact, not UV. Alkyd, waterborne or polyurethane topcoats at sensible film thickness are adequate, and the saving is better spent on valves, supports and walkway areas plus complete marking coverage.
Q6. The colour code was ordered correctly — why does it look wrong on the pipe?
Three variables: gloss (the same formulation at different 60° readings looks lighter or darker), film thickness and hiding (a thin film over a dark substrate reads grey), and substrate colour. Compare like for like — same gloss, same build, same substrate — and judge under both D65 and A before blaming the tinting plant.
Q7. Black pipes blister in summer. Is the coating defective?
Look at temperature and dew point first. Carbon-black films absorb strongly, and differential expansion between coating and steel produces cyclic stress; if the substrate was not at least 3 °C above dew point at application, trapped water vaporises on heating and blisters. IR-reflective dark pigments, a more elastic topcoat or shifting the application window are the practical responses.
9. Sources
- GB 2894-2025, colours for safety signs and safety information (issued 2025-05-30, effective 2026-03-01; supersedes GB 2893-2008, GB 2894-2008 and GB 7231-2003).
- GB 7231-2003, basic identification colours and code indications for industrial pipelines — source of the eight colours, 150 mm band, 10 m pitch and the 25 mm black hazard edges (now withdrawn).
- Public communication of the Guiyang emergency-management authority (2026-03-02); Production Safety Law of the PRC, Articles 35 and 99.
- GB/T 3181 standard colours of paint films; GB/T 1766 rating of paint deterioration; GB/T 1865 / ISO 4892-2 xenon exposure; GB/T 9754 and ISO 2813 gloss; GB/T 3979 and GB/T 11186 colorimetry; GB/T 9286 and GB/T 5210 adhesion; GB/T 9276 climatic annex.
- ISO 12944-1/-2/-5/-6/-9: environment classes, systems, durability L < 7 a, M 7–15 a, H 15–25 a, VH > 25 a.
- ISO 20560-1:2024 and ISO 20560-2:2023 (safety information for piping and tanks), ISO 3864-1:2011, ISO 17398:2004.
- GB 30981-2020 and GB 30981.1/.2-2025 (effective 2026-06-01); the 4 % consumption tax above 420 g/L VOC in the ready-to-spray state.
- HG/T 4749-2014 mixed metal oxide pigments and HG/T 4755-2014 polysiloxane coatings (numbers as published; verify against the official texts).
- Natural exposure data from the National Material Environmental Corrosion Platform (Wanning station) and published studies on fluoropolymer weathering, as cited in industry reviews.
Last updated: 2026-10-19 | Prepared by the technical team of Kexin New Materials (Guangdong) Co., Ltd. This article interprets publicly available standards and literature; colour codes, band dimensions and acceptance limits must be confirmed against the official text of GB 2894-2025 and the project specification, and coating systems against product data sheets and field trials.