Compreender a ASTM B117 para Máquinas de Teste de Spray de Sal
Data de publicação:12/05/2025 Categoria:Artigos técnicos Visualizações:10802
Understanding ASTM B117 for Salt Spray Test Machines: Setup, Compliance, and Best Practices
The definitive procurement and operations reference for ASTM B117 neutral salt spray (fog) testing — covering chamber design, solution preparation, specimen mounting, and the differences between ASTM B117, ISO 9227, and ASTM G85.
At a Glance
Why ASTM B117 Remains the Reference Salt Spray Standard
History, scope, and the cost of running B117 incorrectly
ASTM B117 — the Standard Practice for Operating Salt Spray (Fog) Apparatus — has been the dominant corrosion test standard for over a century. First published in 1939, it specifies the apparatus, test solution, operating conditions, and procedures for neutral salt spray (NSS) testing of metallic and non-metallic coatings. Despite the rise of more realistic cyclic corrosion tests like ASTM G85 and GM9540P, B117 remains the most-cited salt spray test in specifications across automotive, fastener, coating, and electronics industries.
A salt spray test machine for ASTM B117 compliance is a controlled environment chamber that atomizes a 5% sodium chloride solution into a fine mist, maintains chamber temperature at 35°C ± 1°C, and continuously exposes test specimens to this corrosive fog. The standard does not specify pass/fail criteria — it specifies how to run the test. Pass/fail criteria come from the product specification (e.g., 240 hours with no red rust = ASTM B117 + spec).
Derui Salt Spray Chamber: ASTM B117 Compliance Specs
Chamber, atomization, and control specifications
Chamber & Air System
Solution & Specimen
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Long-term reliability and operator safety considerations
Construction Quality
Look for a chamber with a 5–10 mm PP or FRP wall thickness, a sloped lid (so condensation drips back into the chamber rather than onto specimens), a pneumatic lid lift (reduces operator strain), and an observation window with a heating element to prevent fogging. Chamber interior should be smooth and free of crevices that can trap salt deposits and contaminate future tests.
Routine Maintenance
Atomizer nozzles should be inspected weekly for clogging — clean with ultrasonic bath or replace. The saturator tower should be drained and refilled monthly. The solution tank should be drained and refilled with fresh solution every 7 days. The chamber interior should be rinsed and dried between test runs. With proper maintenance, a Derui salt spray chamber runs 3000+ hours continuously without issues.
Safety Considerations
Salt spray is highly corrosive to surrounding equipment. The chamber should be installed in a well-ventilated area with exhaust to the building exterior (not recirculated). The exhaust air contains 5% NaCl droplets that will damage electronics, metal furniture, and HVAC ductwork. Operators should wear safety glasses, nitrile gloves, and lab coats when handling salt solution or removing specimens. Solution disposal must comply with local wastewater regulations (NaCl is not hazardous, but the volume warrants drain permits in most jurisdictions).
Perguntas Frequentes
ASTM B117 setup, operation, and result interpretation
How long should I run ASTM B117?
Duration is defined by your product spec or customer requirement. Common durations: 24h (basic coatings), 96h (decorative chrome), 240h (zinc plating), 480h (heavy-duty marine), 1000h (military per MIL-A-8625). The chamber can run continuously; you set the timer and remove specimens at the specified interval.
Qual é a diferença entre a ASTM B117 e a ISO 9227?
For NSS (neutral salt spray), they are functionally equivalent: 5% NaCl, 35°C, 1–2 mL/80cm²/h. Differences are editorial and testing-house preference. ISO 9227 is more commonly cited in Europe; ASTM B117 in North America. For AASS (acetic acid) and CASS (copper-accelerated), only ISO 9227 defines them — ASTM uses G85 variants.
What pH should the collected spray be?
6.5–7.2 for ASTM B117 NSS. Measure the pH of the spray collected in a clean beaker placed in the chamber (not the solution in the tank, which can differ). Adjust with dilute HCl (lower pH) or NaOH (raise pH). Recheck daily.
Can I run ASTM B117 and ASTM G85 in the same chamber?
Yes. The chamber hardware is the same. ASTM G85 A1 (acetic acid salt spray) uses the same atomizer and temperature; G85 A3 (prohesion) uses a different solution and a heated soak cycle. Most modern chambers support both via a programmable profile.
Why is my ASTM B117 test failing despite following the standard?
Most common causes: (1) atomizer clogged or dirty, (2) chamber temperature out of spec, (3) spray rate not 1–2 mL/80cm²/h, (4) solution pH drift, (5) specimen preparation inconsistent. Run the ASTM B117 §11 verification (temperature uniformity, spray rate, pH) before re-testing. Our Derui chambers include a verification procedure on the controller.
What is the cost of ASTM B117 chamber?
A 270 L ASTM B117 compliant chamber starts at $3,500–$5,000. 480 L chambers run $5,500–$9,000. Larger 800–2000 L walk-in chambers run $12,000–$30,000+. Pricing varies with control sophistication, data logging, and accessories. Contact Derui for a quote based on your chamber size and standard requirements.
