What is NACE and why it matters in industrial corrosion protection
NACE standards are widely referenced in corrosion control for heavy-duty industrial assets, and many have been maintained and published through AMPP as joint SSPC/NACE standards.
For EPC and owner teams, the value of NACE coating standards is that they define what “acceptable surface” looks like, which is the foundation for adhesion, durability, and predictable inspection acceptance.
Decision rule: if your spec only says “SP10” but does not define surface profile, soluble contamination control, and inspection records, you do not yet have a buildable requirement.
NACE surface preparation standards explained
Surface preparation standards are the most re-used NACE references in coatings, because they set a visible acceptance condition that can be audited.
NACE No. 1 / SP5: White metal blast cleaning
White metal blast cleaning targets the highest level of abrasive blast cleanliness, intended to remove visible contaminants, mill scale, rust, and old coatings so the surface is uniformly clean.
It is commonly specified for very severe corrosion environments where the extra cost is justified by risk and consequence of failure.
NACE No. 2 / SP10: Near-white metal blast cleaning
Near-white metal blast cleaning is commonly used when the objective is to remove rust, mill scale, and coatings while allowing limited staining, making it a frequent “workhorse” requirement for Oil & Gas steel.
In the joint SSPC-SP 10/NACE No. 2 definition, staining is limited to no more than 5% of each unit area of surface.
NACE No. 3 / SP6: Commercial blast cleaning
Commercial blast cleaning provides a lower degree of cleaning than SP10 and allows significantly more staining, which can be appropriate for less severe exposure or less critical assets.
In the SSPC/NACE joint comparison, commercial blast cleaning allows staining on up to 33% of each unit area of surface.
NACE SP2 and SP3: Hand and power tool cleaning
Hand and power tool cleaning standards are used for maintenance, repairs, and situations where full abrasive blasting is not feasible.
They are not a “cheap substitute” for blast grades when long life and high severity exposure are required, because they do not deliver the same uniformity and profile control.
NACE vs ISO surface preparation comparison
Engineers often map NACE and ISO terms to communicate across regions, but equivalence should be treated as a practical translation, not a guarantee of identical outcomes.
A commonly used mapping is SP5 approximately aligning with Sa 3, SP10 approximately aligning with Sa 2.5, and SP6 approximately aligning with Sa 2, but acceptance still depends on written definitions, visual standards, and the project’s verification plan.
Spec tip: always state the standard and the verification method you will use on site, because “equivalent” language without inspection criteria leads to disputes.
Understanding corrosion severity in NACE-based projects
NACE-based projects often define severity through environment description, corrosion mechanisms, and asset consequence, rather than a single atmospheric category label.
For offshore and coastal assets, contamination control and maintenance access constraints usually dominate the coating strategy, because rework and shutdown costs are high.
Use zone logic your RFQ can support:
- Offshore platform zones: splash, weather deck, sheltered areas, and crevice-rich details.
- Refinery steel: pipe racks, hot zones, chemical splash areas, and under-insulation interfaces.
- Tank farms: exterior atmospheric zones, roof areas, and high-condensation regions.
Typical coating systems for Oil and Gas projects using NACE prep
Below are system directions that help procurement compare bids without locking into one brand.
- Offshore steel with SP10 or SP5: corrosion-control primer direction plus high-build barrier coats and a durable topcoat, with strict stripe coat and inspection density at edges and welds.
- Refinery steel and pipe racks: high-build epoxy barrier direction where access is complex and downtime is costly, with repair rules and intercoat controls defined in the ITP.
- Storage tank exteriors: epoxy-based barrier build direction with finish selected for UV and weathering expectations, and surface prep grade aligned to severity and budget strategy.
- Buried pipelines: select pipeline-specific coating technologies and define surface prep and holiday testing expectations in the scope, because buried failures are high consequence.
For heavy-duty system architectures and where they fit in industrial projects, reference this internal page once for scope alignment: Heavy Duty Anti-Corrosion Coatings for Industrial Projects.
NACE inspection and quality control requirements that prevent rework
NACE-style projects succeed when you control what the inspector can verify.
- Soluble salt and contamination checks: define test method, frequency, and acceptance in the ITP so “salt control” is not left to assumptions.
- Surface profile and cleanliness: state the target profile range required by the coating system and the method of verification.
- DFT control by layer: specify DFT ranges by coat and require higher reading density at edges, welds, and repairs.
- Dew point discipline: require documented ambient and steel temperature checks to prevent condensation-related adhesion loss.
Use this internal checklist structure to standardize what gets inspected and recorded on steel structure projects: Steel Structure Coating Inspection Checklist.
Common mistakes when following NACE standards
- Writing SP10 but not stating surface profile requirements or the verification method, which creates contractor-to-inspector disputes.
- Ignoring soluble contamination control in coastal and offshore work, then seeing early blistering or adhesion loss.
- Specifying DFT totals but not defining DFT ranges by layer and by detail, which hides thin edges until corrosion appears.
- Using SP6 where SP10 or SP5 is justified by severity and consequence, especially offshore and severe industrial exposures.
Troubleshooting tip: when early failure occurs, audit prep acceptance records and environmental logs first, then review stripe coat compliance and repair procedure execution.
How to choose a NACE-compliant coating system
Use a process that creates comparable bids and inspectable deliverables.
- Define the corrosion environment and split the asset into zones.
- Select the surface preparation grade per zone and state profile and acceptance criteria.
- Choose the coating system architecture by function, corrosion control, barrier build, and weathering resistance.
- Define DFT ranges by layer and specify stripe coat requirements for edges and welds.
- Build the QC dossier, hold points, inspection frequency, and repair rules into the RFQ.
NACE vs ISO 12944: which should you follow?
Many global projects use both, ISO 12944 to structure environment and durability planning and NACE or SSPC/AMPP standards to define surface preparation and inspection deliverables in a way contractors can execute.
The practical rule is to follow the client’s governing specification, then ensure your RFQ includes the missing “execution details” that make standards implementable on site.
External reference for the current standards ecosystem and definitions: see AMPP’s standard listing for near-white metal blast cleaning. AMPP Standards
Practical recommendations for NACE-based projects
- Add a pre-job conference checklist: surface prep acceptance, profile checks, salt testing plan, dew point logging, and repair method agreement.
- Require inspection records as deliverables: DFT by layer, climate logs, and repair logs should be part of handover, not an optional extra.
- Make “equivalence” explicit: when you translate between ISO and NACE terms, state both the written standard and the acceptance method.
CTA
Contact us for NACE-compliant coating system recommendations for offshore, refinery, or tank farm projects, and request a TDS pack and system recommendation via Contact Industrial Coating Manufacturer.
Technical Note
All guidance is for engineering and budgeting support; final surface preparation grade, profile, inspection criteria, DFT ranges, and coating system selection must be confirmed by the governing project specification and the relevant product TDS.
