ISO 12671:2021

Overview - ISO 12671:2021 (Thermal spraying, symbolic representation on drawings)

ISO 12671:2021 defines how thermally sprayed coatings are indicated on technical drawings. It standardizes a compact symbolic system (an elementary symbol plus supplementary symbols and complementary indications) so designers and manufacturers can communicate coating type, process, materials, thickness and post-treatments without overloading drawings. The second edition (2021) updates designation examples in line with current thermal‑spray terminology and material standards.

Key topics and requirements

• Elementary symbol: the basic identifier for a thermally sprayed coating (commonly shown as “TS” above the reference line).
• Supplementary symbols: identify coating function (e.g., BC = bond coat, TC = top coat) and post‑treatments.
• Process symbol: indicates spraying method (for example APS = atmospheric plasma spraying, PFS = powder flame spraying, X = free choice of process).
• Spray material designation: referenced to ISO 14232-1 (powders) or ISO 14919 (wires); latest edition applies if no date is given.
• Thickness and condition: coating thickness (e.g., “250 ± 50 µm”) and condition (as = as‑sprayed, f = fused, m/c = machined) are shown in the designation.
• Placement on drawings: complete symbol includes a designation outside the part outline, an arrow line, and a continuous reference line with the symbol above it; a tail can separate bond and top coats.
• Area representation: coated regions are shown with broad dashed‑dot lines; permitted or excluded areas use specific line styles and masking symbols for workshop drawings.
• Parts’ list and patents: when multiple drawings use a parts list, a position number may replace full instructions; patent‑protected processes can be referenced by trade name or parts‑list entry.
• Dimensioning & tolerances: indicate size/position of coating area and roughness tolerances for post‑treatments; general tolerances apply unless specified.

Applications and who uses it

ISO 12671:2021 is used by:

• Design and CAD engineers preparing assembly and part drawings
• Coating engineers and process planners specifying layers and treatments
• Quality/inspection teams defining thickness and surface tolerances
• Procurement/spec writers and manufacturers interpreting contract requirements Practical use cases include specifying thin or multi‑layer thermal spray systems, aligning machining allowances after coating, and ensuring consistent communication across suppliers and workshops.

Related standards

• ISO 14232-1: Thermal spraying - Powders
• ISO 14919: Thermal spraying - Wires, rods and cords
• ISO 14917: Thermal spraying - Terminology, classification
• ISO 128-2, ISO 1302: drawing and surface‑texture conventions

Keywords: ISO 12671:2021, thermal spraying, thermally sprayed coatings, symbolic representation on drawings, coating designation, spray material, coating thickness, technical drawings.