ASTM B117 Salt Spray and Corrosion Compliance Testing
ASTM B117 testing is a salt spray exposure method used to evaluate how metallic materials, coatings, and plated finishes resist corrosion in a controlled salt fog environment.
Summary Of ASTM B117 Testing
It is widely used to compare coating systems, confirm process stability, and screen materials before qualification programs move forward.
Most outcomes are based on visual and dimensional indicators such as red rust on steel, white corrosion products on zinc, blistering, underfilm corrosion, staining, and coating breakdown. A failure typically means corrosion exceeds the acceptance criteria tied to a drawing, OEM specification, or internal engineering requirement. A deviation is documented when a nonconformance occurs but the program chooses to continue testing for diagnostic value, or when the requirement source is unclear and must be resolved before a final compliance decision.
Retesting is usually triggered by a confirmed failure, a change in surface preparation, a coating line adjustment, a supplier change, or evidence that the sample set was not production intent. When retest occurs, configuration control matters as much as chamber time because small differences in edges, scribe method, or coating thickness can shift the corrosion pattern.
ASTM B117 testing often supports compliance packages that require clear traceability, documented exposure conditions, and consistent inspection practices. Reports also need to show how acceptance criteria were applied, how inspections were performed, and how any anomalies were handled so results hold up during customer reviews and audits.
When ASTM B117 Testing Is Required Or Recommended
ASTM B117 testing is commonly required at product launch gates, during coating or plating qualification, and after a design change that alters material selection, coating stackup, or joint geometry. It is also used when incoming quality trends shift, when field returns show corrosion at fasteners or interfaces, or when supplier changes introduce new pretreatment chemistry, bath control limits, or cure profiles.
Severity is shaped by the intended service environment and how the product traps moisture and salts. Edge conditions, crevices, dissimilar metal contact, and coating porosity can create worst case features that corrode faster than broad surfaces. Sample selection should represent those worst case details so exposure time produces meaningful differentiation.
Teams often choose between qualification, verification, validation, and production lot testing based on the decision that needs support. Qualification builds confidence in a design and process window, verification confirms a change did not create new risk, validation shows performance under defined use conditions, and lot testing focuses on ongoing manufacturing control. Worst case configuration typically means the thinnest coating thickness within tolerance, the most aggressive edge condition, and the assembly state that creates the highest chance of retained salt solution.
The Importance Of ASTM B117 Testing
ASTM B117 testing exists because corrosion is one of the most common drivers of cosmetic degradation, functional loss, and long-term reliability issues in plated and coated components. It helps quality teams identify process drift before parts reach production vehicles, industrial equipment, or outdoor enclosures. It also supports engineering decisions when multiple coatings appear similar on paper but behave differently in practice.
For engineering leadership, the value is decision clarity. Salt spray results can reduce warranty exposure by showing which finish systems fail early, and they can support design margin decisions when results are paired with thickness data, adhesion checks, and post exposure functional evaluations. These results also improve supplier alignment by turning subjective corrosion concerns into repeatable observations tied to controlled exposure conditions.
Documentation quality is essential because corrosion testing is often reviewed by customers who want traceability. Reports must show sample configuration, surface condition, exposure duration, chamber parameters, inspection timing, and the requirement source that defines acceptance. Without those elements, two programs can report the same hours but reach different conclusions.
Common Risks Reduced By ASTM B117 Testing
Common risks include red rust on steel substrates, white corrosion on zinc coatings, blistering and delamination from poor surface preparation, and undercutting at scribes or edges. Galvanic interactions can also appear when dissimilar metals are assembled, especially near fasteners, seams, and joints where electrolyte retention is higher.
Tests expose weak links because salt fog steadily deposits chlorides that drive corrosion reactions, and the exposure environment makes it easier to see coating defects that may be missed in short term handling. Preconditioning steps, controlled scribe methods, and defined inspection intervals help separate a robust coating system from one that only looks acceptable at the start of exposure.
How ASTM B117 Testing Data Supports Pass/Fail Decisions
Data commonly includes exposure duration, chamber conditions, and detailed visual inspection results at defined checkpoints. Depending on the requirement source, evaluations can include percent area corrosion, maximum creep from a scribe, edge undercut length, blister size and density, staining, and changes in coating appearance.
Acceptance criteria and tolerances should be explicitly stated before the run starts. When results fall near a threshold, engineering judgement often relies on consistent inspection method, repeatability of the observation, and whether the corrosion pattern matches expected failure modes. Deviations should be captured with photos and clear notes rather than rewording results to fit a target outcome.
Measurement confidence also depends on chamber control and instrument calibration for any supporting measurements. When failures occur, effective reporting documents probable drivers such as coating defects, localized thin film areas, improper masking, or edge condition. That information supports corrective action planning and makes retest more efficient.
Scope Of ASTM B117 Compliance Testing
Pretest Planning, Sample Selection, And Incoming Evaluation
Pretest planning starts with defining production intent samples, worst case features, and any required scribes, edge exposures, or assembly states. Incoming evaluation typically includes labeling, photos, baseline visual inspection, and any agreed baseline measurements such as coating thickness checks or functional verification.
Configuration control should capture surface preparation, coating system, cure condition, masking approach, and mounting method. The plan should also confirm inspection timing, acceptance criteria source, and how anomalies will be recorded so the final report aligns with customer and internal quality requirements.
Test Execution, Monitoring, And Quality Controls
ASTM B117 testing uses a controlled salt fog generated from a sodium chloride solution delivered through atomizing nozzles into a closed chamber. Key controls include solution concentration, pH, chamber temperature, fog collection rate, and specimen positioning so deposition remains uniform across the exposure zone. Samples are mounted to avoid direct liquid impingement and to prevent droplets from one specimen contaminating another.
Chamber monitoring includes frequent checks of temperature and fog collection volumes using collection funnels and graduated cylinders placed in specified locations. Solution pH and concentration are verified at defined intervals because drift can change corrosion rate and shift results. Quality controls also include cleaning and maintenance practices that prevent buildup, nozzle clogging, or contamination that alters deposit chemistry.
Exposure duration is recorded continuously, and inspections are performed at agreed checkpoints without compromising the test. Handling during interim inspections should avoid wiping or disturbing corrosion products unless the requirement source explicitly allows cleaning before evaluation. Photo documentation should use consistent lighting and angles to support comparisons across time points and across programs.
Data Reduction, Analysis, And Result Validation
Raw observations become reportable results through structured inspection records, photo logs, and criteria based scoring. When creep from a scribe or percent corrosion is required, measurements should use consistent rulers, overlays, or image based measurement methods that are documented in the report. Any calculations should be traceable and reproducible.
Validation relies on chamber performance checks, review of collection rate and pH data, and confirmation that specimen placement followed the plan. When results are unexpected, repeat runs may be justified for root cause isolation, especially when sample preparation history is uncertain. Instrument calibration status should be verified for any supporting measurements included in the compliance decision.
Pass fail logic should follow the requirement source first, then documented engineering assessment boundaries when criteria are incomplete. If deviations occur, they should be listed clearly with the reason, the impact on compliance, and any follow up actions such as additional exposure time or supplemental inspection.
Documentation And Reporting Requirements
Reports should capture chamber identification, exposure duration, solution chemistry controls, temperature, collection rate results, and inspection schedule. Sample configuration should include material, coating system, surface preparation, any scribes or edges evaluated, and mounting orientation. Photo evidence should show initial condition and each inspection checkpoint with traceable file naming.
The report should reference the test method as ASTM B117 Testing and identify the requirement source that defines acceptance criteria, such as an OEM specification or drawing note. Acceptance criteria should be stated in measurable terms, and results should be presented in the same structure as the criteria so reviewers can confirm compliance quickly.
Compliance packages often need revision control, traceability to sample identifiers, and approvals or signatures tied to laboratory quality systems. When programs include multiple standards, the report should separate method requirements from customer-specific criteria so the basis of the compliance decision is clear.
Related EMC And Electrical Test Services
Some corrosion programs include powered assemblies, mixed material stacks, and harness interfaces where corrosion products can increase resistance or cause intermittent faults. When that risk exists, pairing corrosion work with Electrical Load And Transient Testing can help confirm the assembly still meets functional requirements under defined electrical stress conditions.
For electronics that must meet conducted transient requirements, post exposure evaluations can also reference standards based electrical methods such as ISO 7637-2 Conducted Immunity On Power Lines Supply Voltage Transients or ISO 7637-2 Conducted Transient Emissions Testing. For broader electromagnetic compatibility needs, OEM Or Component EMC Validation can complement corrosion testing when the product must maintain performance after environmental exposure.
Frequently Asked Questions About ASTM B117 Testing
How Many Samples Are Typically Needed For ASTM B117 Testing
Sample count depends on the requirement source and whether multiple finishes, lots, or worst case configurations are being compared. Many programs include replicates per condition to separate process variation from true coating performance.
What Causes Early Failures In Salt Spray Exposure
Common drivers include poor surface preparation, thin coating areas at edges, porosity, contamination from handling, and inadequate cure. Assembly crevices can also hold solution and accelerate corrosion at joints.
Does More Hours Always Mean Better Corrosion Performance
Longer exposure can improve differentiation, but hours alone do not guarantee correlation to field life. Results are most useful when tied to defined acceptance criteria and paired with an understanding of the expected failure mode.
How Are Scribes And Edges Evaluated
Many specifications focus on undercut and creep from a scribe because it challenges coating adhesion and barrier performance. Edge evaluation often targets corrosion initiation where coating thickness and coverage are most variable.
What Documentation Is Needed For A Compliance Package
A complete package typically includes the method reference, exposure conditions, solution controls, specimen configuration, inspection records, photos, acceptance criteria source, and a clear pass fail statement.
Expert Laboratory Testing For ASTM B117 Testing
Applus+ Laboratories and A+ Laboratories support corrosion programs that require repeatable chamber control, disciplined configuration control, and reporting that is built for customer review. ASTM B117 testing is included within the accredited mechanical scope for corrosion and salt spray work, supporting consistent methods and quality system practices aligned to ISO IEC 17025.
Reliable Analysis can help define sample configurations, inspection timing, and documentation structure so results support clear compliance decisions. Related corrosion services such as ASTM B368 Corrosion Salt Spray CASS Testing and SAE J2334 Corrosion Salt Spray Testing can also be scoped when a program needs alternate exposures or cyclic severity, and ASTM D2247 Humidity Testing can be added when moisture driven degradation is part of the risk profile.
Request a quote to start ASTM B117 testing for a defined finish system, exposure duration, and reporting package that supports compliance decisions for customer requirements.
