Measurement of metal-surface rust removal (and painting, anti-corrosion): routed by object - plant and piping by area m2, metal structures by theoretical mass t/kg - with the companion rule of matching the unit of the quota item applied

Topic Positioning

This card sets out the measurement of metal-surface rust removal (and the painting, anti-corrosion that follow): not an either-or between "area or mass" but a routing by object - plant and piping by design-shown surface area in m2, metal structures by theoretical mass - with the final check against the unit of the quota item applied. Use with the companion card on rust grades and item conversion factors.

Core Conclusions

1. The basic routing by object (DB11/T 2382-2024 Construction Works Consumption Quota Standard, section 6.12 painting, anti-corrosion and insulation works; clause wording)

• 6.12.8 plant and piping rust-removal quantities are computed by area on the design-shown surface dimensions.
• 6.12.9 metal-structure rust-removal quantities are computed on the theoretical mass of the structure.
• 6.12.15 pipe painting by area on the design-shown surface; 6.12.16 plant and rectangular duct painting by area on the design-shown surface; 6.12.17 metal-structure and pipe-hanger painting on the theoretical mass of the structure or hanger; 6.12.18 painting of ash, cloth and mastic faces by design-shown surface area.
• 6.12.22 plant and piping anti-corrosion by design-shown surface area; for internal walls, where thickness is 10 mm or more compute on the inside diameter, under 10 mm on the outside diameter. 6.12.23 metal-structure anti-corrosion on the theoretical mass of the structure.
• 6.12.11 painting consumption includes manual rust removal and comprehends painting of all fittings, plant manholes and nozzle irregularities.
• 6.12.28 plant and piping insulation assumes insulation after erection; where insulated before erection, the labour consumption is preferably multiplied by 0.90.
• 6.12.43 each field-joint coating band is 400 mm on pipes below 426 mm OD and 600 mm above 426 mm; 6.12.44 nozzle painting and anti-corrosion quantities are computed on the design-shown count.
• Insulation and protective finishes split volume / area: 6.12.34 plant insulation by design-shown volume; 6.12.35 pipe insulation by design-shown volume; 6.12.36 ventilation duct insulation on the clear duct area; 6.12.37 valve and flange insulation by design-shown volume; 6.12.39 damp-proof courses and protective finishes on the design-shown insulation surface area; 6.12.40 insulation trays and hooks on metal-structure mass, insulation boxes on design-shown surface area; 6.12.41 pipe anti-condensation on design-shown volume.

2. A further split inside metal structures (GB/T 50856-2024 quantity take-off standard for general building services, Annex M table M.1.1 painting works, code 031201, notes)

• Note 8: general steelwork (hangers, supports, brackets, ladders, railings, platforms) and pipe-rack steelwork measure in kg; steelwork of sections over 300 mm and H sections over 300 mm measure in m2 on developed area.
• Note 5: the surface areas of plant shells and piping include fittings, valves, flanges, manholes and nozzle irregularities.
• Note 4: plant shell and pipe surface area S = pi x D x L, with pi the circular constant, D the diameter and L the shell height or pipe linear metres.
• Note 6: for plant with dished ends S = L x pi x D + (D2/2)2 x pi x K x N, K = 1.5, N the number of ends.
• Note 1: measured in metres on the centreline in linear metres, without deducting lengths of attached structures, fittings and valves.
• Note 2: painted parts are the surfaces of plant, piping etc.; note 3: metal-structure types are general steelwork, pipe-rack steelwork, H-section steelwork etc.
• Note 7: steelwork made of steel pipe paints under the pipe-painting codes; steelwork of rolled sections under the metal-structure painting codes.

3. The municipal basis is the same stock (DB11/T 2382-2024 clause 7.4.51)

Rust removal and painting set items separately for piping, steelwork and metal structures: pipe rust removal and painting on the design-shown pipe surface area; steelwork rust removal on the design-shown theoretical mass; metal-structure painting on the design-shown theoretical mass. Companion clauses (same section): 7.4.52 field anti-corrosion of steel pipes preferably sets items by coating material and diameter - coal-tar epoxy with glass cloth, inorganic zinc-rich, zinc-rich plus PU composite, and cement-mortar linings by length on design-shown dimensions; heat-shrink sleeves and three-layer PE tape by weld-joint count; 7.4.53 field anti-corrosion at pipe joints (except heat-shrink sleeves / tape) follows 7.4.52 with labour multiplied by 1.10; 7.4.54 field insulation - insulation layer by design-shown volume, protective finish by design-shown surface area.

4. Local corroboration

1. SJG 181.4-2024 Municipal Consumption Quota Standard, Volume 4 water supply and drainage networks, clause 1.2.17: pipe rust removal and painting and plant painting on the design-shown developed area in m2; metal-component painting on mass in kg. External anti-corrosion on the design pipe-centreline length (supply: fittings, valves and flanges not deducted; drainage: manhole-centre to manhole-centre less manhole lengths) times the pipe girth in m2; internal anti-corrosion by centreline length in m (mechanical centrifugal and manual coating) or length times internal girth in m2 (epoxy); radiation cross-linked PE heat-shrink sleeves by the piece; pipe-weld X-ray inspection by the film.
2. SJG 84-2020 Municipal Maintenance Consumption Quota Standard, Volume 2 water and drainage maintenance, 5.2.8: manual rust removal of miscellaneous shaped steel components (supports, hangers, brackets, stair flights, railings, walkway plates, platforms) and pipe-rack steelwork on component mass in kg; plant and piping, silo grille platforms and other large steelwork by power-tool rust removal on the design-shown component surface area in m2.
3. Match the unit of measurement to the unit of the item: metal-structure rust-removal items commonly price per t or per 100 kg (e.g. TB/T 10831-2024 Volume 10, chapter 1 section 6 item 6, mechanical rust removal FY-745 sand-blast and FY-746 shot-blast, both per t); pipe / plant rust-removal and painting items commonly per m2, 10 m2 or 100 m2 (e.g. TB/T 10833-2024 Volume 12, chapter 7 section 2 manual rust-removal items per 10 m2).
4. Converting where mass and area bases differ: some local quotas give mass-to-area reference factors (Shaanxi 2024 consultation draft table 14-4: steel fence gates, railings and window grilles 64.98; steel ladders 44.84; stepped steel stairs 39.90; light roof trusses 53.20; miscellaneous ironwork 58.00) for conversion where the item unit differs from the quantity basis.

5. Working order

First fix the object (plant / piping / metal structure / large steelwork) - then the basis (area m2 or theoretical mass t, kg) - then check the unit of the intended item against it, converting per the quota's rules or switching to an item of that basis where mismatched; fittings, valves, flanges, manholes and nozzle irregularities are comprehended in the items and never added.

Applicability Boundaries

• Rust-removal quantities follow the DESIGN-SHOWN dimensions, not as-built surfaces or actual mass (SJG 181.4-2024 clause 1.1.11 item 5: secondary rust removal arising from construction needs is computed where occurring; factory-finished pipe already coated takes no rust-removal, painting or anti-corrosion items).
• "By theoretical mass" addresses general steelwork and pipe-rack steelwork; single sections over 300 mm and H sections over 300 mm switch to developed area m2 - the split most often missed in practice.
• Fittings, valves, flanges, manholes and nozzle irregularities are comprehended in the items (DB11/T 2382-2024 6.12.11; SJG 181.4-2024 clause 1.1.11 item 4) and not added when computing shell / pipe area by S = pi x D x L; but where the volume provides otherwise (field joints by count, sleeves by weld count), that prevails.
• Scopes differ: DB11/T 2382-2024 is the Beijing consumption standard; SJG 84-2020 and SJG 181.4-2024 are Shenzhen (SJG) standards; TB/T 10831-2024 and TB/T 10833-2024 railway sector budget quotas; the Shaanxi figures come from the 2024 consultation draft, not the published text. Cross-region / cross-sector borrowing requires checking the volume's general notes and chapter notes.
• This card covers measurement only, not rust grades and item conversion factors (how to multiply where the design grade differs from the item's compiled grade - see the related card).

Further Reading

• DB11/T 2382-2024 Construction Works Consumption Quota Standard, section 6.12 (6.12.8 / 6.12.9 / 6.12.11 / 6.12.15-6.12.18 / 6.12.22 / 6.12.23 / 6.12.34-6.12.44) and section 7.4 network works, clauses 7.4.50 to 7.4.55
• GB/T 50856-2024 quantity take-off standard for general building services, Annex M painting, anti-corrosion and insulation works, table M.1.1 painting works (code 031201), notes
• SJG 181.4-2024 Municipal Consumption Quota Standard, Volume 4 water supply and drainage networks, clauses 1.1.11 and 1.2.17
• SJG 84-2020 Municipal Maintenance Consumption Quota Standard, Volume 2 water and drainage maintenance, clause 5.2.8
• TB/T 10831-2024 Railway Works Budget Quota Manual, Volume 10 building works, chapter 1 section 6 item 6 mechanical rust removal; TB/T 10833-2024 Volume 12, chapter 7 section 2 rust removal and coating
• Shaanxi new consumption quota (2024 consultation draft), tables 14-4 and 14-5, measurement rules and factors