Как написать спецификацию на подготовку поверхности, которая даёт результат

A surface preparation specification is not a formality. It is the legal and technical framework within which coating contractors work, inspectors verify, and warranty claims are evaluated. A poorly written specification produces ambiguity at every stage, and ambiguity in coating projects usually resolves in the direction of less preparation, not more. A well-written specification eliminates guesswork, establishes clear inspection hold points, and creates an auditable record that protects the asset owner when coating systems fail to perform.

This guide covers the twelve elements a complete surface preparation specification must contain, how to state the right standards, the common specification weaknesses that create risk, example clause language, and the documentation that must accompany coating project execution. For the contractual side, see what makes a coating specification enforceable.

What must a surface preparation specification include?

A complete, enforceable surface preparation specification includes all of the following elements. Missing any one creates a gap that will be exploited, either through contractor interpretation or through disputes when performance falls short.

1. Scope of work and substrate definition

Define precisely what is to be prepared. This includes:

• Structural members and components to be coated (and explicitly, what is not to be coated)
• Current condition of the substrate: rust grade (ISO 8501-1 A–D), existing coating condition, known contamination
• Any areas requiring special treatment (welds, edges, crevices, bolt holes, pitted areas)
• Areas where the standard preparation method cannot be applied and what alternative is required

2. Surface preparation standard

State the required SSPC (or ISO) surface preparation standard by full designation, not just by name. "Near-white blast" is not a specification. "SSPC-SP 10/NACE No. 2 Near-White Metal Blast Cleaning" is a specification. The distinction matters when disputes arise over what was actually required. The full ladder of grades is set out in our complete guide to SSPC surface preparation standards.

If different standards apply to different areas or components (for example SP 10 on primary structure and SP 11 on weld repairs), define these separately and clearly. Do not leave the contractor to interpret which standard applies where.

3. Surface preparation method

In addition to the cleanliness standard, specify whether a particular method is required or prohibited:

• Is abrasive blasting required, or may power tool preparation be used if it achieves the specified result? If power tools are allowed, name the power tool grade (SSPC-SP 11 or SP 15) or the cleanliness and profile to be achieved. The 2018 paper on defining surface preparation standards with power tools shows why "power tool cleaning" alone is not enough: different tools produce very different results.
• Is wet abrasive blasting or water jetting permitted? If so, what flash rust level is acceptable?
• Are there ATEX or hot-work restrictions that prohibit specific methods?
• Is containment required? Who is responsible for it and what are the requirements?

4. Abrasive media specification (if blast cleaning is required)

Where abrasive blasting is specified, define:

• Acceptable abrasive types (steel grit, steel shot, mineral abrasive, or combinations)
• Abrasive size range and angular or rounded shape
• Water-soluble contamination limits for the abrasive, tested by conductivity per ASTM D4940, with the limit taken from the applicable SSPC-AB or ISO 11126 abrasive standard
• Whether recycled abrasive is permitted and what testing is required before reuse

5. Anchor profile requirement

State the required anchor profile range in µm (or mils; 25.4 µm = 1 mil). Do not rely on the blast cleaning standard to define this: blast standards define cleanliness, not profile. The profile requirement comes from the coating system TDS and must be explicitly stated in the specification, with the measurement method:

"The prepared surface shall have an anchor profile in the range of 50–85 µm as measured per ASTM D4417 Method C using Testex Press-O-Film® X-Coarse replica tape and a calibrated spring micrometer."

How to take and record those readings is covered in our anchor profile measurement field guide.

6. Soluble salt contamination limit

For any project in a marine, offshore or industrial atmospheric environment, define the maximum acceptable soluble salt level after preparation. State the test method, typically Bresle patch extraction per ISO 8502-6 with conductometric measurement per ISO 8502-9. The conductivity of the extract is measured in µS/cm and converted to a surface density of soluble salts, usually expressed in mg/m² (or µg/cm²; 10 mg/m² = 1 µg/cm²) as NaCl equivalent. Then state the specific limit. A specification that does not reference salt contamination is incomplete for any coating project where coating longevity matters. Why this matters is explained in soluble salt contamination and coating failure.

7. Environmental conditions for preparation and coating

Define the environmental limits within which surface preparation and coating application may proceed:

• Maximum relative humidity (commonly 85%, lower for sensitive applications or where the TDS requires it)
• Minimum steel temperature above dew point (commonly 3°C)
• Minimum and maximum air and steel temperature for coating application
• Required measurement intervals and instruments
• Stop-work criteria: what happens when conditions go out of range mid-operation

8. Maximum interval from preparation to priming

State the maximum time between completion of surface preparation and application of the first coat of primer. This prevents rust-back of prepared steel before coating. There is no single standard value; the following are common project practice and must be aligned with the TDS and site conditions:

• Dry abrasive blasting in normal conditions: around 4 hours
• Dry abrasive blasting in high humidity or marine environments: shorter, often 2 hours or less
• Water jetting: as soon as the surface has dried to the acceptable flash rust level
• Power tool preparation in dry conditions: typically the same day, often within 4–8 hours

In every case, any visible rust-back before priming should require the surface to be re-prepared.

9. Inspection hold points

Define the mandatory inspection hold points: points at which work must stop and inspection must be completed before the next phase can begin. At minimum, specify hold points for:

• After surface preparation, before priming: visual cleanliness, anchor profile, environmental conditions, salt contamination (where required)
• After primer application: dry film thickness, visual appearance, adhesion testing (if specified)
• After each subsequent coat: dry film thickness, intercoat contamination check
• Final inspection after topcoat: total DFT, holiday detection (for immersion service), visual appearance

Witness hold points (inspector must be present) and review hold points (records must be reviewed and approved) should be distinguished in the specification. A full sequence is set out in coating inspection: the 11 hold points that prevent most failures.

10. Verification methods and instruments

Do not leave the inspection method to contractor interpretation. State explicitly:

• Visual standard for cleanliness: SSPC-VIS 1 (abrasive blast cleaning) or SSPC-VIS 3 (hand and power tool cleaning), or the ISO 8501-1 photographs; specify which, based on the preparation method
• Profile measurement: ASTM D4417 Method C (replica tape, with tape grade and micrometer type) or Method B (depth micrometer)
• Salt contamination on the steel surface: ISO 8502-6 extraction and ISO 8502-9 conductivity, or another method from SSPC Guide 15, with instrument and calibration
• Abrasive contamination: ASTM D4940
• DFT measurement: SSPC-PA 2 or equivalent, instrument type and calibration requirement

11. Contractor and inspector qualifications

State the minimum qualifications required for coating contractors and inspection personnel. AMPP (formed from SSPC and NACE) runs widely recognised certification programmes:

• Coating inspectors: AMPP Coating Inspector Program (CIP) Level 1, 2 or 3
• Field painting contractors: SSPC-QP 1 (and QP 2 where hazardous paint removal is involved); shop painting: SSPC-QP 3
• Industrial coating applicators: relevant AMPP or owner-specific qualification

12. Documentation requirements

Specify what records must be created, by whom, in what format, and within what timeframe. At minimum, require:

• Daily inspection reports signed by a qualified inspector
• Environmental condition logs (RH, steel temperature, dew point, air temperature) at defined intervals
• Anchor profile measurement records with location, date, tape grade, readings and mean
• Salt contamination test records where required
• DFT records per SSPC-PA 2
• Non-conformance reports for any area that fails inspection, and records of remediation
• Abrasive media certificates and contamination test results

What are the most common specification weaknesses?

Specifying the standard without specifying the profile

The most common gap. "SSPC-SP 10" tells the contractor what cleanliness to achieve. It does not tell them what anchor profile to produce. If the specification does not state an anchor profile requirement, the contractor has no obligation to achieve one, and the profile may be inadequate for the coating system.

No salt contamination requirement

Failing to specify a maximum salt level means there is no enforceable standard against which contamination can be rejected. This is a critical omission for any offshore, marine or industrial project with long repainting intervals.

Vague scope definition

"All structural steel" is not a specification. Drawings must show exactly what is to be prepared and coated, what is not, and what treatment applies to transitions, edges and crevices where standard methods cannot reach.

No hold points

A specification without defined inspection hold points allows coating application to proceed before inspection. If the inspector is not present at the critical verification stages, non-conformance cannot be caught before the evidence is covered by primer.

Conflicting TDS and specification requirements

When the coating TDS specifies a minimum of SP 10 and the project specification states SP 6, there is a conflict. In disputes the more stringent requirement often prevails, but who bears the cost of rework is a contractual question. Resolve conflicts before work begins, not during or after.

Example specification clause language

The following is example specification language for a high-performance industrial coating application requiring near-white blast cleaning on primary structure with power tool preparation for spot repairs. The values are illustrative; take the actual limits from the coating TDS and the service environment.

3.1 Surface Preparation — Primary Structure: Steel surfaces shall be prepared to SSPC-SP 10/NACE No. 2 Near-White Metal Blast Cleaning. The anchor profile shall be in the range 50–90 µm as measured per ASTM D4417 Method C. Abrasive media shall be angular steel grit capable of producing the specified profile. Recycled abrasive shall be tested per ASTM D4940 and replaced when conductivity exceeds the limit of the applicable SSPC-AB abrasive standard.

3.2 Surface Preparation — Spot Repairs and Inaccessible Areas: Areas inaccessible to blast equipment, and localised repair areas not exceeding 0.5 m² per location, shall be prepared to SSPC-SP 11 Power Tool Cleaning to Bare Metal. The anchor profile shall be a minimum of 40 µm as measured per ASTM D4417 Method B or C. (SSPC-SP 11 itself requires a minimum of 25 µm / 1 mil; state a higher value where the coating requires it.)

3.3 Soluble Salt Contamination: The prepared surface shall have a maximum soluble salt contamination of 50 mg/m² (5 µg/cm²) NaCl equivalent, determined by Bresle patch extraction per ISO 8502-6 and conductivity measurement per ISO 8502-9. One test shall be taken per 10 m² of prepared surface area, with additional tests at any area of known or suspected contamination.

3.4 Hold Point: Surface preparation inspection per Items 3.1–3.3 above is a mandatory witness hold point. The coating applicator shall not apply primer to any area until the inspector has verified compliance in writing.

Clause 3.3 uses the same numerical limit that IMO PSPC sets for dedicated seawater ballast tanks. Atmospheric service may allow a higher value and some immersion specifications require less, so always take the figure from the coating data sheet.

Key takeaways

• A complete surface preparation specification defines: cleanliness standard, method constraints, anchor profile requirement, salt contamination limit, environmental conditions, preparation-to-priming interval, inspection hold points, verification methods and documentation requirements. All elements are required.
• State the full SSPC/NACE or ISO designation, not just the common name, and state it separately for each substrate area or condition where different requirements apply.
• Anchor profile is not defined by the cleanliness standard. It must be stated explicitly, with the measurement method and tape grade.
• Mandatory inspection hold points before priming are the most important enforcement mechanism in any coating specification. Without them, non-conformance goes undetected until failure occurs.
• Specification conflicts must be resolved before work begins. The most common conflict is between the project specification and the coating product TDS; verify both and align them before issuing for tender.

Frequently asked questions

What must a surface preparation specification include?

At minimum: scope and substrate condition, the cleanliness standard by full designation for each area, permitted and prohibited methods, abrasive requirements, anchor profile range and measurement method, soluble salt limit and test method, environmental limits, maximum time to priming, inspection hold points, verification instruments, personnel qualifications and documentation requirements.

Does SSPC-SP 10 define the required anchor profile?

No. Blast cleaning standards such as SSPC-SP 10 and ISO 8501-1 Sa 2½ define visual cleanliness only. The anchor profile range comes from the coating manufacturer's technical data sheet and must be written into the specification separately, together with the measurement method, for example ASTM D4417 Method C replica tape.

What soluble salt limit should a coating specification state?

Take the limit from the coating data sheet and the service environment, and state the test method. Published examples include 50 mg/m² NaCl equivalent for ballast tanks under IMO PSPC, and US Navy limits of 3 µg/cm² chloride for immersion and 5 µg/cm² for non-immersion service.

Can a specification allow power tools instead of abrasive blasting?

Yes, if it specifies the result rather than only the method. SSPC-SP 11 and SSPC-SP 15 are power tool standards that require bare metal and a minimum 25 µm (1 mil) profile. Where a blast-equivalent finish is needed, state the cleanliness and profile required and confirm acceptance of the method with the coating manufacturer.

Related articles

• SSPC-SP 10 Near-White Metal Blast: Complete Technical Guide
• SSPC-SP 11 Power Tool Cleaning to Bare Metal
• SSPC-SP 6 vs SP 10: Which Standard Does Your Project Need?