Resonate Testing provides ISO 9227 salt spray testing for corrosion resistance, coating validation and product durability programmes across the UK and Ireland.
ISO 9227 is an international salt spray corrosion test standard used to assess the comparative corrosion resistance of materials, metallic coatings, paint systems, fasteners, enclosures and finished assemblies. Test specimens are placed in a controlled chamber and exposed to a continuous salt fog for an agreed duration.
The standard includes neutral salt spray (NSS), acetic acid salt spray (AASS) and copper-accelerated acetic acid salt spray (CASS) methods. Conditions such as salt solution, pH, chamber temperature, fallout rate, specimen orientation and inspection intervals should be confirmed before the test starts so the final report supports the customer specification or drawing requirement.
Engineer-led ISO 9227 corrosion testing for aerospace, defence, manufacturing, electronics and advanced engineering teams. Resonate Testing helps define the right salt spray method, exposure duration, inspection intervals and reporting evidence before testing begins.
ASTM B117 Salt Spray Testing
Ready to plan an ISO 9227 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.
Required ISO 9227 Salt Spray Solution
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, rain and temperature testing
ISO 9227 is an international salt spray corrosion test standard used to assess the comparative corrosion resistance of materials, metallic coatings, paint systems, fasteners, enclosures and finished assemblies. Test specimens are placed in a controlled chamber and exposed to a continuous salt fog for an agreed duration.
The standard includes neutral salt spray (NSS), acetic acid salt spray (AASS) and copper-accelerated acetic acid salt spray (CASS) methods. Conditions such as salt solution, pH, chamber temperature, fallout rate, specimen orientation and inspection intervals should be confirmed before the test starts so the final report supports the customer specification or drawing requirement.
| Reference | Typical relevance |
|---|---|
| ASTM B117 | Neutral Salt Spray Corrosion Standard |
ISO 9227 defines three recognised salt spray test methods. The right method depends on the material, coating system, customer specification and evidence required.
ISO 9227 is commonly discussed alongside other corrosion and salt spray standards, including ASTM B117 and customer-specific automotive, aerospace, defence or coating specifications. The correct reference depends on the product, coating system, market and acceptance criteria.
The most commonly used corrosion test, NSS exposes samples to a fine mist of 5% sodium chloride solution at 35°C. It is suitable for metals, metallic coatings and painted components, providing a method of assessing corrosion resistance and coating quality.
AASS uses the same salt solution as NSS but with the addition of acetic acid to create a more aggressive environment. This method is primarily used for decorative copper, nickel and chromium coating systems as well as certain aluminium finishes where a faster assessment of coating performance is required.
CASS is the most severe of the three ISO 9227 methods. It uses acetic acid and copper chloride dihydrate to create a more aggressive salt fog. The test is conducted at 50°C and is typically used to evaluate high-performance decorative coatings and specialised surface treatments where enhanced durability is required.
| Standard | General | pH | Specific Gravity | Conductivity (µS/cm) | Notes |
|---|---|---|---|---|---|
|
NSS (Neutral Salt Spray) – ISO9227:2022 |
5% Solution, 50g/l +- 5g/l, with max 0.5% Impurities by mass | 6.5 to 7.2 @ 25°C | 1.029 to 1.036 @ 25°C + – 2°C | No more than 20 µS/cm |
|
| AASS (Acetic Acid Salt Spray) – ISO9227:2022 | 5% Solution, 50g/l +- 5g/l, with max 0.5% Impurities by mass | 3.0 to 3.3 @ 25°C | 1.029 to 1.036 @ 25°C + – 2°C | No more than 20 µS/cm |
|
| CASS (Copper Accelerated Salt Spray) – ISO9227:2022 | 5% Solution, 50g/l +- 5g/l, with max 0.5% Impurities by mass | 3.0 to 3.3 @ 25°C | 1.029 to 1.036 @ 25°C + – 2°C | No more than 20 µS/cm |
|
Salt spray testing is carried out by placing specimens within a corrosion test chamber that complies with the requirements of ISO 9227, Section 4 (Apparatus), and is operated in accordance with Section 8 (Operating Conditions) of the same standard.
The test solution is prepared by dissolving high-purity sodium chloride in purified water to produce a solution containing 5% sodium chloride and 95% water by mass. The purity of both the salt and water should meet the requirements specified in ASTM B117 as it is the more stringent specification.
Depending on the test method being employed, the solution is prepared in accordance with Section 3 of ISO 9227. The three principal test variants are:
Before the test specimens are introduced, the chamber is stabilised at the specified operating temperature of 35°C and adjusted to produce the required salt fog deposition rate. The fallout rate is verified using a minimum of two collection devices, each consisting of an 80 cm² funnel connected to a graduated measuring cylinder. For each spray atomiser, one collector is positioned close to the atomiser and the other at a more distant location. These collectors are installed at approximately the same height as the test specimens and positioned in accordance with ASTM B117, while also considering the effective working area defined by the chamber manufacturer.
This test is commonly used to evaluate the corrosion resistance of coated and uncoated metal components when subjected to a salt-laden atmosphere under controlled elevated-temperature conditions.
Performance is assessed by observing the development of corrosion products, including white rust and red rust, following exposure for a defined period. The duration of testing varies according to the expected corrosion resistance of the material or coating under evaluation. Generally, coatings that provide greater protection against corrosion will require longer exposure periods before any visible signs of oxidation or corrosion are detected.
Typical application areas include:
Automotive
Aerospace & Defence
Marine & Offshore
Electronics
Coatings / Paints
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 / ISO 9227
Expose: Run the 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 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.
It is an accelerated laboratory exposure, not a direct prediction of outdoor service life. Results are best used for comparison, screening or customer-defined acceptance.
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 pausing or interruption unless required.
Inspection may record red rust, white corrosion, blistering, coating breakdown, creep from scribe, staining, photographs and other agreed observations.
Inspections can be completed before exposure, at agreed interim points and after exposure, depending on the customer requirement and quotation scope.
Acceptance criteria are normally defined by the customer specification, drawing note, coating standard or agreed qualification requirement, not by ISO 9227 alone.
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.
Share your corrosion testing requirement, coating specification, drawings, sample details or inspection criteria. Resonate Testing can review the salt spray method, test duration and reporting evidence needed for your programme.
Whether you’re looking to contact us for the first time or have another testing requirement, we’d love to hear from you.
