How to Specify Powder Coating on Drawings: Callouts, Standards, Color Codes, and Finish Designations

A powder coating specification on a drawing is a contract between the designer and the coating applicator. It defines exactly what the finished surface should look like, how it should perform, and what standards it must meet. A vague or incomplete specification — "powder coat black" — leaves critical decisions to the coater's interpretation and creates the conditions for disputes when the finished product does not meet the designer's unstated expectations. Was the black supposed to be matte or gloss? RAL 9005 jet black or RAL 9011 graphite black? Polyester for outdoor use or epoxy for interior? 60 microns or 100 microns? Without clear specification, the coater has no way to know.

A well-written powder coating specification eliminates ambiguity by defining every parameter that affects the appearance and performance of the finished coating. It references recognized standards that both parties understand, specifies measurable acceptance criteria, and identifies the testing methods used to verify compliance. This level of clarity protects both the specifier (who gets the product they intended) and the coater (who has clear targets to work toward and documented evidence of compliance).

Why Proper Specification Matters

The effort invested in writing a proper specification pays dividends throughout the project. It reduces requests for information during bidding, minimizes rework and rejection during production, provides a clear basis for resolving any quality disputes, and creates a documented record that supports warranty claims if coating performance issues arise during service. This article explains how to write powder coating specifications for both architectural and engineering drawings.

Essential Elements of a Powder Coating Callout

A complete powder coating callout on a drawing should include the following elements, each addressing a specific aspect of the coating requirement. Not every element is needed for every application, but omitting a critical element invites misinterpretation.

Coating type identifies the technology: "Thermosetting powder coating" or simply "Powder coating" distinguishes it from liquid paint, anodizing, or other finishing methods. Resin system specifies the chemistry: polyester, super-durable polyester, epoxy, hybrid, polyurethane, or fluoropolymer. This determines the fundamental performance characteristics, particularly UV resistance and chemical resistance.

Color is specified using a recognized color standard: RAL Classic (e.g., RAL 7016), RAL Design, NCS, Pantone, or a manufacturer's proprietary code. Always include the color standard name and number — "dark grey" is not a specification. Gloss level is specified as a target value with tolerance at a defined measurement angle: "30 ± 5 GU at 60°" is precise; "satin" is not.

Film thickness defines the minimum and/or target coating thickness: "Min. 60 µm" or "60-80 µm." Performance standard references the applicable quality certification or test standard: Qualicoat Class 1 or 2, GSB Standard or Master, AAMA 2603/2604/2605, or project-specific test requirements. Pretreatment standard may be specified separately or included by reference to the performance standard.

A complete callout might read: "Powder coating: Super-durable polyester, RAL 7016, 30 ± 5 GU at 60°, min. 60 µm, to Qualicoat Class 2." This single line communicates everything the coater needs to know.

Referencing Standards: Qualicoat, GSB, and AAMA

Referencing a recognized quality standard in your specification is the most efficient way to define a comprehensive set of performance requirements without writing pages of custom test criteria. The major architectural powder coating standards — Qualicoat, GSB, and AAMA — each define requirements for pretreatment, powder quality, application, film thickness, adhesion, hardness, impact resistance, and accelerated weathering. By referencing one of these standards, you incorporate all of their requirements by reference.

Qualicoat is the dominant European architectural quality label. Qualicoat Class 1 requires 1,000 hours of accelerated weathering with limited gloss and color change. Qualicoat Class 2 requires 2,000 hours and is specified for high-exposure applications. Qualicoat Class 3 is the newest tier, requiring 3,000 hours for the most demanding environments. Qualicoat Seaside adds additional salt spray requirements for coastal installations. Specifying "to Qualicoat Class 2" on a drawing incorporates all of Qualicoat's pretreatment, application, and testing requirements.

AAMA specifications are the North American equivalent. AAMA 2603 is the basic performance tier for general commercial use. AAMA 2604 is the intermediate tier requiring 3,000 hours of South Florida weathering exposure. AAMA 2605 is the premium tier requiring 10,000 hours of South Florida exposure — the most demanding architectural coating standard in the world. Specifying "to AAMA 2605" communicates a premium performance requirement that any qualified North American coater will understand.

GSB International offers Standard and Master certification levels, with GSB Master representing performance comparable to Qualicoat Class 2. When specifying for international projects, note which standard applies and ensure the selected coater holds the relevant certification.

Color Specification Best Practices

Color specification is the area most prone to misunderstanding and disputes, and it deserves particular attention. The golden rule is: always specify color using a recognized, numbered color standard — never rely on descriptive names alone. "Anthracite grey" could refer to RAL 7016, RAL 7021, RAL 7024, or any number of proprietary colors depending on who is reading the specification.

RAL Classic is the most widely used color standard in the powder coating industry, with over 200 colors identified by four-digit codes (e.g., RAL 9010 Pure White, RAL 7016 Anthracite Grey). RAL Design offers a larger palette of approximately 1,825 colors organized by hue, lightness, and chroma, using seven-digit codes (e.g., RAL 260 50 30). NCS (Natural Colour System) is popular in Scandinavian countries and uses a notation based on perceived color attributes. Pantone is widely used in graphic design and product design but less common in architectural specification.

For custom colors that do not match a standard reference, provide a physical color sample — a painted panel, a material sample, or a previously coated part — that the powder manufacturer can match instrumentally. Specify the acceptable color difference tolerance using Delta E (ΔE) values: ΔE ≤ 1.0 is a tight match visible only to trained observers under controlled conditions; ΔE ≤ 2.0 is a standard commercial match acceptable for most applications; ΔE ≤ 3.0 is a loose match that may show visible differences between adjacent parts.

Always specify the gloss level alongside the color, as the same pigment formulation appears different at different gloss levels. A color match performed at one gloss level may not be acceptable at a different gloss level. If the project involves multiple coaters or multiple powder batches, require all parties to match against the same physical reference standard and specify the maximum acceptable ΔE between batches.

Finish Designations and Special Requirements

Beyond color and gloss, drawings may need to specify additional finish characteristics. Texture type should be identified if a textured finish is required — wrinkle, hammer-tone, sand, leather, or river vein — along with a reference sample showing the acceptable texture range. Metallic effect finishes should reference the specific powder product code, as metallic effects cannot be adequately communicated through color codes alone.

Masking requirements identify areas that must remain uncoated — threaded holes, mating surfaces, electrical contact points, or areas that will receive a different finish. These should be clearly dimensioned on the drawing with a note such as "Mask — do not coat" or "Leave bare metal." Specify the masking method tolerance — how precisely the coating boundary must align with the drawing dimension — as tight masking tolerances add cost.

Multi-color or multi-finish requirements should be clearly indicated on the drawing with separate callouts for each color zone and dimensioned boundaries between zones. Specify the acceptable transition width between colors — a sharp, clean line requires precision masking, while a slight overlap or feathered edge may be acceptable and less costly to achieve.

Special performance requirements beyond the referenced standard should be listed explicitly. These might include specific chemical resistance requirements (resistance to cleaning agents, solvents, or industrial chemicals), enhanced abrasion resistance, anti-graffiti properties, antimicrobial performance, or electrical insulation requirements. Each special requirement should reference a test method and acceptance criterion so the coater knows exactly what is expected and how compliance will be verified.

Drawing Callout Formats and Examples

The format of powder coating callouts on drawings varies by industry convention and company standards, but clarity and completeness are universal requirements. Here are several example callout formats for different application types.

For architectural aluminum: "FINISH: Powder coating, super-durable polyester, RAL 7016 Anthracite Grey, 30 ± 5 GU at 60°, min. 60 µm DFT, to Qualicoat Class 2. Applicator must hold current Qualicoat license." This callout defines every critical parameter and requires the coater to be certified.

For general industrial equipment: "COATING: Thermosetting powder coating, polyester, RAL 5012 Light Blue, 70 ± 10 GU at 60°, 60-80 µm DFT. Pretreatment: Iron phosphate conversion coating. Adhesion: Gt 0-1 per ISO 2409. Salt spray: Min. 500 hours per ISO 9227 without blistering or corrosion creep > 2 mm from scribe."

For automotive components: "POWDER COAT: Polyester-TGIC, Manufacturer XYZ Product Code ABC-123, 80 ± 10 GU at 60°, 70-90 µm DFT. Clear topcoat: Manufacturer XYZ Product Code DEF-456, min. 40 µm DFT. Total system DFT: 110-130 µm. Adhesion: Gt 0 per ISO 2409 after 240 hours humidity exposure per ISO 6270-1."

For military/defense applications: "COATING: Powder coating per MIL-PRF-32348, Type II, Color 383 per FED-STD-595, max. 5 GU at 60°. Pretreatment per MIL-DTL-5541 Type II (non-chromate) for aluminum substrates. All requirements of MIL-PRF-32348 apply."

Each example includes the essential elements — coating type, resin, color, gloss, thickness, and performance standard — tailored to the specific application context.

Common Specification Mistakes to Avoid

Several common mistakes in powder coating specification lead to quality problems, cost overruns, and disputes. Recognizing and avoiding these mistakes saves time and money for everyone involved.

Specifying color by name only — "black," "white," "grey" — without a color standard reference is the most common and most easily avoided mistake. There are dozens of blacks, whites, and greys in the RAL system alone, and each looks distinctly different. Always include a color code.

Omitting the gloss level leaves the coater to choose, and their default may not match your expectation. If you do not specify gloss, you will get whatever the coater's standard product provides in that color, which may be high gloss when you wanted matte or vice versa.

Specifying an inappropriate resin system for the application environment is a technical error with long-term consequences. Epoxy powder coatings specified for exterior use will chalk and fade within months. Polyester specified for chemical immersion service may not provide adequate resistance. Match the resin system to the service environment.

Over-specifying creates unnecessary cost. Requiring AAMA 2605 performance for an interior application, or specifying ΔE ≤ 0.5 color tolerance for industrial equipment, adds cost without adding value. Specify what the application actually requires, not the tightest tolerance available.

Failing to specify pretreatment requirements — or assuming the coater will choose an appropriate pretreatment — is a risk. If coating longevity is important, specify the pretreatment type or reference a standard that defines pretreatment requirements. The pretreatment is invisible in the finished product but determines its long-term performance.

Integrating Specifications into Project Documentation

For large projects — particularly architectural projects with multiple building elements, colors, and finish types — the powder coating specification should be documented in a dedicated specification section rather than relying solely on drawing callouts. This specification section provides the detailed requirements that drawing callouts reference, keeping the drawings clean while ensuring comprehensive coverage.

In architectural projects following CSI MasterFormat, powder coating specifications typically fall under Section 09 96 00 (High-Performance Coatings) or Section 05 05 00 (Common Work Results for Metals) depending on the project structure. The specification section should include: scope of work, applicable standards and references, quality assurance requirements (coater certifications, quality management systems), materials (powder type, color, gloss, manufacturer), surface preparation requirements, application requirements (film thickness, cure schedule), inspection and testing requirements, and warranty requirements.

Drawing callouts then reference the specification section: "Powder coating per Section 09 96 00, Color A" — where Color A is defined in the specification section with full details. This approach allows multiple drawing sheets to reference the same specification without repeating the full callout on every sheet, and it provides a single location for specification changes during the project.

For smaller projects or non-architectural applications, a comprehensive drawing callout combined with a referenced standard (Qualicoat, AAMA, or a company-specific coating specification) may be sufficient. The key principle is that every parameter affecting coating appearance and performance should be defined somewhere in the project documentation — either on the drawing, in a specification section, or in a referenced standard.