Resonate Testing supports corrosion, coating and product durability assessments using ASTM B117 NSS (Neutral Salt Spray) exposure, helping teams understand how materials, finishes and assemblies perform in controlled corrosive conditions.
ASTM B117 is the internationally recognised standard for salt spray corrosion testing. It establishes a controlled method for assessing the corrosion resistance of metals, coatings and surface finishes by exposing test samples to a continuous salt fog environment. Widely used across the automotive, aerospace, marine and manufacturing industries, ASTM B117 helps manufacturers evaluate coating performance, compare material durability and support quality assurance programmes.
The test involves placing specimens in an enclosed chamber where they are exposed to a continuous indirect neutral saline water, producing a fine fog or mist. The fallout rate is controlled between 1.0 and 2.0 ml per 80 cm² per hour, with the chamber temperature maintained at + 35°C. In addition to this the pH of the fallout must be within the range of 6.5 to 7.2. Chamber conditions are held at a constant steady state for the duration of the test, which can be varied as required.
Resonate provides engineer-led environmental testing for aerospace, defence, manufacturing, electronics and advanced engineering programmes. ASTM B117 salt spray testing supports corrosion resistance assessment for materials, coatings, fasteners, enclosures and finished products where exposure duration, inspection points and reporting evidence must be clearly agreed.
ISO 9227 Salt Spray Testing: Corrosion Testing for Coatings, Metals & Components
Ready to plan an ASTM B117 Salt Spray Test Campaign? Send your requirements, material specifications, exposure time and other information for an engineer to review.
Corrosion testing works best when the exposure duration, specimen orientation, inspection method and pass/fail criteria are clear before the chamber is loaded. Early review helps avoid delays and makes sure the final evidence matches the requirement.
Share your material, coating system, drawings, required test duration, inspection criteria and any customer specification. Resonate Testing can review setup, handling and reporting expectations before quotation.
ASTM B117 neutral salt spray exposure
Coating, plating and surface treatment assessment
Pre-test photography and agreed inspection points
Customer specification and acceptance criteria review
Environmental test campaign planning alongside IP, humidity and temperature testing
ASTM B117 defines the requirements for a neutral salt spray environment and positioning of test specimens, but it does not by itself define many important factors for a test, such as:
The required exposure duration
Inspection schedule and criteria
Acceptance criteria
Specimen Conditions
In order to accurately assess your product for corrosion resistance, accurate guidelines in terms of both specific methodology (such as exposure time) and acceptance criteria must be provided as to what is deemed a “Pass” or “Fail”, (I.e, what / quantity of corrosion products on a material is deemed acceptable). This information must be provided via a customer specification, coating standard, drawing note or qualification plan.
| Reference | Typical relevance |
|---|---|
| ISO 9227 |
Salt Spray Testing: Corrosion Testing for Coatings, Metals & Components, (NSS, AASS, CASS) |
Resonate Testing provides engineer-led environmental testing support for aerospace, defence, electronics, manufacturing and advanced engineering customers across the UK and Ireland. ASTM B117 programmes can support coating comparison, production validation, customer acceptance and corrosion resistance assessment depending on the agreed specification.
The laboratory supports development, validation and compliance testing for materials, coated parts, fasteners, enclosures, assemblies and products where controlled environmental exposure evidence is required. Test activity can be planned against ASTM B117 and customer-defined inspection requirements.
An ASTM B117 Salt Spray test program is carried out by exposing test samples within a corrosion chamber that complies with the design requirements of ASTM B117 and is operated under the conditions prescribed by the standard. The neutral salt solution is produced from a solution containing 5% sodium chloride and 95% water by weight. Both the salt and water used in preparing the solution must satisfy the purity requirements specified in ASTM B117 shown below:
| Standard | General | pH (Measured Temp) | Specific Gravity *Using Salinity Hydrometer* | Conductivity in µS/cm | Notes |
|---|---|---|---|---|---|
| ASTM B117 | 5% Solution, 50g/l +- 5g/l, with max 0.3% Impurities by mass. | 6.5 to 7.2 @ 23°C +-3°C | 4 to 6% @ 25°C | No more than 5.0 µS/cm | Type IV Water from D1193 (Deionised, Electrodeionisation, Reverse Osmosis Water. pH 5.0 to 8.0)
NaCl (I.e Ascott CorroSalt) Reagent Grade NaOH or HCl if pH needs adjustment |
For example the water quality must be of Type IV Water from D1193, which has a stricter limit on conductivity compared to ISO 9227. Prior to the introduction of the test specimens, the chamber is brought to the required operating temperature of 35°C and adjusted to achieve the correct salt spray collection rate.
Verification of the salt fog fallout rate is undertaken by the use of a minimum 2x 80cm2 funnel per atomiser, the funnel discharges into a graduated cylinder in which the solution can be measured. The collectors are installed within the chamber at approximately the same level as the test specimens. In accordance with ASTM B117, one collector will be positioned near the atomiser and another at a more distant location. Their exact placement will also take account of the chamber manufacturer’s defined test area to ensure representative measurement of salt fog fallout throughout the working space.
For coated components and production parts, sample handling and orientation are central to the quality of the test. Drawings, coating callouts, critical faces, masked areas, edges and drainage paths should be reviewed early so the item is exposed in a way that reflects the agreed requirement.
Early engagement helps identify practical issues such as sample size, mixed materials, sharp edges, contact points, fastener assemblies and inspection evidence before the test campaign starts.
Salt spray exposure can highlight coating defects, porous finishes, edge protection issues, galvanic effects, damaged surfaces and areas where corrosion starts around fasteners, cut edges or scribe marks.
Inspection expectations should be agreed early if the requirement refers to red rust, white corrosion, blistering, creepage from scribe, coating adhesion or cosmetic appearance. Clear criteria help avoid subjective interpretation after exposure.
Plan: Review the requirement, exposure duration, specimen details, acceptance criteria and reporting needs.
Prepare: Confirm cleaning, masking, labelling, scribing, orientation and photographic evidence where required.
Load samples: Place specimens so exposed faces, drainage and separation match the agreed setup from customer specifications / ASTM B117.
Expose: Run the neutral salt spray exposure for the specified duration under controlled chamber conditions.
Inspect: Complete agreed interim or final inspections without changing the acceptance criteria mid-test.
Document: Record corrosion observations, coating condition, photographs and any agreed deviations.
Report: Provide the agreed test evidence, observations and summary aligned to the quotation scope.
Part description, material and coating or surface treatment details
Drawings, dimensions and photographs of the parts to be tested
Required ASTM B117 exposure duration
Customer specification, drawing note or acceptance standard
Required inspection intervals, criteria and reporting format
Whether samples need scribing, masking. Confirmation on required cleaning or pre-conditioning procedures.
Critical faces, edges, threaded areas or functional surfaces
Identification of hazardous materials, residues or special handling constraints
Interim inspection points or witness requirements
Photographic evidence and final report expectations
Neutral Salt Fog is 5% Saline Solution with a pH of 6.5 to 7.2, used to create a salt laden environment within a corrosion chamber. The exact specifications of a salt solution may differ between standards.
Any pauses, interim inspections or handling steps should be agreed before testing starts so the final report clearly reflects the test sequence. Generally, the spray must operate continuously without any pasuing or interruption unless required.
Products that need corrosion testing may also need humidity, water ingress, rain, temperature or other environmental assessments. Coordinating the sequence early helps reduce handling friction and keep documentation aligned across the full programme.
For projects that also need environmental testing, review the related services before finalising the sample set and test order.
Outputs are agreed before the test so the evidence matches the programme need. A typical package may include:
Confirmation of the agreed exposure duration and test method
Specimen identification and setup notes
Observations from pre-test, interim and post-test inspections where agreed
Photographic evidence of sample condition where agreed
Recorded corrosion, coating or surface condition observations
An agreed test report or data pack aligned to the quotation scope
Book salt spray testing for coated parts, metals, fasteners, enclosures and assemblies. Use the contact route to share the requirement, exposure duration, drawings, coating details or specification for review.
Whether you’re looking to contact us for the first time or have another testing requirement, we’d love to hear from you.
