Understanding ASTM B117 for Salt Spray Test Machines
Date: 12/05/2025 Categories: Technical articles Views: 4500
What Exactly Is ASTM B117?
When people talk about a “salt spray test,” they’re usually talking about ASTM B117. It’s the global reference point for neutral salt spray (NSS) corrosion testing.
Full Name and Current Revision
| Item | Description |
|---|---|
| Full name | ASTM B117 – Standard Practice for Operating Salt Spray (Fog) Apparatus |
| Current widely used revision | ASTM B117-19 (2019 edition) |
| Test type | Neutral Salt Spray (NSS) using NaCl |
Scope and Purpose
ASTM B117-19 specifies how to run a salt fog test so that results are:
- Repeatable – same lab, different day.
- Comparable – different labs, same standard.
- Objective – fixed conditions, measurable variables.
In simple terms, the practice defines:
- What solution you use (5% sodium chloride).
- What atmosphere you create (salt fog at 35 °C).
- How you expose specimens (angle, time, spray rate).
- How you monitor the test (pH, temperature, fog rate).
The goal is corrosion resistance testing under controlled, aggressive conditions, not reproducing one specific real-world environment.
Environment vs. Equipment
ASTM B117 tells you the performance of the test environment, not what brand of chamber you should buy.
- It defines conditions, such as:
- Salt concentration
- pH range
- Temperature setpoint
- Fog collection rate
- It does not prescribe:
- Chamber size or layout
- Specific nozzle design
- Control system brand
- Data logging software
Standard vs. Salt Spray Chamber
Think of ASTM B117 as the rulebook, and the salt spray machine as the tool you use to follow that rulebook.
| Aspect | ASTM B117-19 (Standard) | Salt Spray Test Chamber (Equipment) |
|---|---|---|
| Role | Defines test conditions and procedures | Creates and maintains the required salt fog environment |
| Owned by | Standards body (ASTM International) | Lab, factory, or test service provider |
| Compliance requirement | Must be followed exactly | Must be capable of meeting all ASTM B117 parameters |
| Changes over time | Updated via ballot/revision | Upgraded or calibrated to keep meeting the standard |
As an equipment provider, my job is simple but strict: **
Core Requirements of ASTM B117 – The Technical Breakdown
When we talk about ASTM B117 salt spray test compliance, these are the non‑negotiables I design around in our chambers.
Salt Solution – 5% Sodium Chloride
ASTM B117 fixes the solution at 5 ± 1% NaCl with controlled purity:
| Item | Requirement | Why it matters |
|---|---|---|
| Salt concentration | 4–6% (target 5% by mass) | Keeps corrosion rate consistent between labs |
| Salt type | High‑purity sodium chloride (NaCl) | Avoids metals/contaminants that skew results |
| Water quality | Distilled or deionized water | Prevents mineral deposits and unexpected corrosion |
If the 5% sodium chloride solution isn’t stable, your corrosion resistance testing data is weak from the start.
pH Range – 6.5 to 7.2
ASTM B117 sets the pH of the salt solution at 6.5–7.2 (neutral salt spray / NSS):
- Neutral pH = neutral salt spray: no acid or alkali boost.
- Keeps results comparable across labs and between batches.
- Drift outside this range will either under‑attack or over‑attack the coating.
I always recommend automatic pH monitoring and regular manual checks.
Chamber Temperature – 35 °C ± 2 °C
Inside the salt spray chamber, the air temperature must be:
- Setpoint: 35 °C
- Tolerance: ± 2 °C (so 33–37 °C)
Why it’s critical:
- Corrosion rate is highly temperature‑dependent.
- Temperature variation across the test zone will cause different results on different panels.
Good chambers hold 35 °C ± 0.5 °C to make life easier during audits and salt spray cabinet calibration.
Fog Collection Rate – 1.0–2.0 mL/h per 80 cm²
ASTM B117 controls how much salt fog reaches the parts:
| Parameter | Requirement |
|---|---|
| Fog collection rate | 1.0–2.0 mL/h per 80 cm² collection area |
| Measurement tool | Collection funnel + graduated cylinder |
| Position | In the exposure zone, away from walls/doors |
Key tips:
- Funnels must be level and not blocked by specimens.
- Check multiple points to confirm uniform fog distribution.
Get this wrong and your salt spray test duration in hours becomes meaningless.
Compressed Air Pressure – 69–172 kPa (10–25 psi)
For proper atomization at the nozzle:
- Pressure range: 69–172 kPa (10–25 psi)
- Air must be clean, oil‑free, and filtered.
- Low pressure = large droplets, wet surfaces.
- High pressure = overly fine mist, unstable fog.
Stable air pressure is one of the easiest ways to stabilize neutral salt spray (NSS) performance.
Specimen Placement Angles – 15°–30° from Vertical
ASTM B117 controls panel angle to keep exposure consistent:
- Panels / flat coupons:
- 15°–30° from vertical, facing the dominant fog direction.
- 3D parts:
- Orient critical surfaces toward the fog.
- Avoid parts shading each other (no “shadowing”).
Use non‑corroding supports (plastic, glass, or suitable polymers) to avoid cross‑contamination.
Continuous Operation and Allowed Interruptions
ASTM B117 is a continuous salt spray test:
- Fog runs non‑stop for the full test duration.
- Allowed short interruptions only for:
- Solution refill
- Chamber checks
- Routine maintenance
Good practice:
- Log every interruption (time, reason).
- Keep doors closed as much as possible; each opening changes temperature, fog rate, and chamber humidity.
If you hold these core ASTM B117 requirements tight, your lab can deliver consistent, trusted corrosion resistance testing results for customers in North America, Europe, and across global markets.
Step-by-step ASTM B117 Salt Spray Test Procedure
1. Prepare the 5% NaCl Salt Solution Correctly
For an ASTM B117 salt spray test, the solution is non‑negotiable:
- Mix ratio: 5 ± 1% sodium chloride (NaCl) by mass in water
- Water quality: distilled or deionized only (no tap water, no minerals)
- Salt quality: high‑purity NaCl, low in heavy metals and impurities
- pH control: adjust to 6.5–7.2 at room temperature using HCl or NaOH
Always measure and record:
- Salinity (by weight or conductivity)
- pH before and during the test
If you’re supplying results to global customers, they will expect these values on every report.
2. Season the Salt Spray Chamber
Before loading parts, the ASTM B117 salt spray chamber must be stable:
- Fill the reservoir with the prepared 5% NaCl solution
- Set chamber temperature to 35 °C ± 2 °C
- Run the chamber empty for at least 30–60 minutes
- Verify:
- Temperature inside the work space
- Fog rate using collection funnels
- Nozzle/atomizer is spraying evenly
I always treat this as a “warm-up cycle” to avoid wasting samples on unstable conditions.
3. Prepare Your Specimens Properly
Poor sample prep will ruin the test, no matter how good the salt spray cabinet is:
- Cleaning: remove oil, dust, fingerprints (solvent clean or mild alkaline wash)
- Masking: protect edges or areas not under evaluation using approved tapes, lacquers, or plugs
- Mounting method: follow the coating or product spec (panels, complete parts, assemblies)
Label each specimen clearly with an ID that survives the test (engraving, stamped tags, neutral plastic labels).
4. Position Panels and Parts per ASTM B117
Correct placement inside the salt spray test chamber is key:
- Angle: mount panels 15°–30° from vertical
- Orientation: test surface facing the main direction of fog
- Avoid:
- Shadowing (one part blocking another)
- Stacking that traps solution
- Contact with metal supports that may corrode
Use plastic, glass, or corrosion‑resistant racks that don’t interact with the salt fog.
5. Set the Test Duration in Hours
ASTM B117 does not tell you how long to run – that comes from your coating spec, customer requirement, or internal standard:
Common practice in global markets:
- Decorative coatings: 24–96 h
- Zinc plating / basic protection: 96–240 h
- High‑performance coatings: 480–1000+ h
Log
Limitations of ASTM B117 Salt Spray Test
Why ASTM B117 Doesn’t Match Real-World Corrosion
ASTM B117 neutral salt spray (NSS) is a simple, constant, aggressive environment:
- Fixed 5% NaCl, fixed 35 °C, no drying, no UV, no dirt, no mechanical damage.
- Real service conditions in Europe, North America, Asia, the Middle East, or coastal regions are cyclic – wet/dry, hot/cold, polluted air, sun, vibration, road salts.
That’s why ASTM B117 salt spray test is great for comparison, but it does not replicate real-world service on its own.
Salt Spray Hours ≠ Service Life
One of the most common mistakes I see in global projects:
“480 hours B117 = 5 years outdoors”
That’s simply not true. There is no universal formula that converts salt spray hours into real-life years because:
- Different coating systems (zinc plating, powder coating, e-coat, paint on aluminum, etc.) react differently.
- Different climates (Nordic road salt, tropical marine, desert) attack materials in different ways.
- ASTM B117 is static, real life is **dynamic
ASTM B117 vs ISO 9227 – key differences engineers must know
When you pick a salt spray standard, you’re really choosing how your corrosion resistance testing will be judged. Here’s how ASTM B117 salt spray test and ISO 9227 neutral salt spray (NSS) compare in real lab use.
Side‑by‑side: ASTM B117 vs ISO 9227 NSS
| Item | ASTM B117 (NSS) | ISO 9227 (NSS) |
|---|---|---|
| Main use region | North America, parts of Asia | Europe, global OEMs, automotive, Asia |
| Solution concentration | 5 ± 1% NaCl | 5 ± 1% NaCl |
| Salt purity | Specifies low impurities, but flexible | Usually tighter impurity limits |
| Water quality | Distilled or deionized | Demineralized / deionized |
| Solution pH at 25 °C | 6.5–7.2 | 6.5–7.2 (stricter recording requirements) |
| Chamber temperature | 35 °C ± 2 °C | 35 °C ± 2 °C |
| Air pressure at nozzle | 69–172 kPa (10–25 psi) | 70–170 kPa (very similar) |
| Fog rate (collection) | 1.0–2.0 mL/h per 80 cm² | 1.0–2.0 mL/h per 80 cm² |
| Fog collection check | Funnels + cylinders, periodic checks | Similar, but more prescriptive in method |
| Acceptance / performance criteria | Given by product or customer spec | Often defined in OEM / product standards |
| Report format | ASTM‑style test report | ISO‑style report, more common in EU OEMs |
Solution, pH, and temperature differences
Both standards run neutral salt spray (NSS) at 5% NaCl and 35 °C, but:
- ISO 9227 tends to:
- Tighten salt purity and water quality rules.
- Expect more formal documentation of pH control and calibration.
- ASTM B117 is:
- Slightly more flexible in raw materials.
- Deeply embedded in legacy specs in the US and Canada.
If you work with global automotive or European OEMs, they’ll almost always call out ISO 9227 directly.
Fog collection and acceptance criteria
Both use a collection funnel and cylinder to control fog rate:
- ASTM B117 salt spray test:
- Fog rate: 1.0–2.0 mL/h per 80 cm².
- Focus is on staying in range; pass/fail is defined in the product/coating spec, not in B117 itself.
- ISO 9227:
- Same fog rate band, but more detail on:
- Where and how to place collectors.
- How often to check and record.
- Many ISO / OEM specs tie exact acceptance criteria and test duration hours to ISO 9227.
- Same fog rate band, but more detail on:
Where each standard is most common
- ASTM B117:
- Standard in North America, especially:
- General industrial coatings.
- Fasteners, hardware, basic metal finishing.
- Widely used in Asia when dealing with US customers.
- Standard in North America, especially:
- ISO 9227:
- Dominant in Europe.
- Strong in global automotive, heavy trucks, and international OEMs.
- Common in South America, Middle East, ASEAN when parts are exported to the EU.
How to choose for your lab and customers
I usually decide like this:
- Go ASTM B117 when:
- Your customers are mainly in USA/Canada.
- You’re doing screening, QC, or benchmarking against US‑style specs.
- Legacy drawings or contracts explicitly say “ASTM B117”.
- Go ISO 9227 when:
- You supply to European or global OEMs (automotive, construction, rail, wind, etc.).
- You want your data to align with international ISO‑based specs.
- Your lab targets global export customers who need ISO reports.
- Best practice for a modern lab:
- Invest in a salt spray chamber that can be calibrated to both ASTM B117 and ISO 9227.
- Keep separate procedures, calibration records, and test report templates for each standard.
- Make it easy for customers in any region to choose the standard that matches their own specs.
If your chamber holds 35 °C tightly, controls fog rate well, and you run proper salt solution, pH, and calibration, hitting both ASTM B117 and ISO 9227 in one lab is straightforward.
How Derui Salt Spray Chambers Guarantee 100% ASTM B117 Compliance
When I design and specify Derui salt spray chambers, I build them around ASTM B117 first, then add everything else. The goal is simple: you press START and you get a clean, repeatable, fully compliant ASTM B117 salt spray test every time.
Precise 35 °C Control Across the Whole Chamber
ASTM B117 neutral salt spray (NSS) requires 35 °C ± 2 °C. I don’t run that close to the limit. Derui chambers are engineered to hold 35 °C ± 0.5 °C uniformly.
How we keep temperature tight:
- Multi‑zone PID control with fast-response sensors
- Optimized airflow design so there are no hot/cold corners
- High‑quality heaters and insulation to avoid drift in long tests (1000+ h)
| Item | ASTM B117 Requirement | Derui Chamber Capability |
|---|---|---|
| Set temperature | 35 °C | 35 °C user set, locked profiles |
| Allowed variation | ± 2 °C | Controlled within ± 0.5 °C |
| Uniformity across workspace | Not explicitly quantified | Validated with mapping reports |
You get stable 35 °C for consistent corrosion resistance testing and reliable comparison between batches, sites, and suppliers.
Patented Nozzle for Stable Salt Fog Distribution
ASTM B117 defines the salt spray environment, not the brand of chamber, so I focus heavily on fog quality:
- Patented atomizer / nozzle for very fine, uniform droplets
- Stable compressed air control to keep fog rate within spec
- No clogging design to support long continuous salt spray tests
This gives you consistent fog collection rate in the required 1.0–2.0 mL/h per 80 cm² range without constant tweaking.
Automated Monitoring & Alarms (pH, Salinity, Temperature, Fog Rate)
Running ASTM B117 manually is painful and risky. That’s why I automate the key checks:
- Solution salinity monitoring (around 5 ± 1% NaCl)
- pH tracking to keep the salt solution within 6.5–7.2
- Real‑time chamber temperature display and logging
- Fog rate monitoring with guided funnel test prompts
If anything drifts out of the ASTM B117 window, the system:
- Triggers visual and audible alarms
- Can pause the test (if you choose)
- Logs the event for your test report and audits
This is especially useful for 24/7 labs, automotive suppliers, and global customers who need rock-solid traceability.
Third‑Party Calibration for ASTM B117 & ISO 9227
To support ISO 9001, OEM audits, and external approvals, I back the hardware with independent calibration:
- Temperature, humidity (if CCT), fog rate, and sensors calibrated by accredited labs
- ASTM B117 and ISO 9227 calibration/verification reports
- Optional annual service contracts for global customers
You can hand over salt spray cabinet calibration documents to your customers or auditors with confidence.
Chamber Sizes from 100 L to 3000 L
Different markets, different needs. I cover the full range:
| Size Type | Volume Approx. | Typical Use Case |
|---|---|---|
| 100–250 L | Benchtop | R&D, universities, small batch testing |
| 400–1000 L | Floor‑standing | Coating qualification, automotive Tier‑1 suppliers |
| 1500–3000 L | Walk‑in/drive‑in | Large parts, assemblies, OEM labs, heavy industry |
All sizes maintain ASTM B117 environment: 5% NaCl, 35 °C, controlled fog, correct specimen exposure.
ASTM B117 + CCT Upgrade Options
Many customers now run both neutral salt spray (NSS) and cyclic corrosion testing (CCT) on the same platform. I design Derui chambers so you can:
- Start with a pure ASTM B117 salt spray cabinet
- Later upgrade to add:
- Drying cycles
- Condensation / humidity
- Air purge
- Multiple corrosion cycles (CCT) profiles
Even after upgrading, you can still run standard ASTM B117 NSS with full compliance. One chamber, multiple standards: ASTM B117, ISO 9227, CCT, OEM specs (e.g. GMW, VW, etc.) depending on your configuration.
In short, Derui salt spray chambers are built so you don’t have to “chase” ASTM B117. The chamber holds temperature, pH, salinity, and fog rate where the standard demands, and the automation, calibration, and sizing options match how global labs actually work today.
Common Failures to Avoid in ASTM B117 Salt Spray Tests
When I run an ASTM B117 salt spray test, my goal is simple: repeatable, defensible data. These are the mistakes that quietly destroy test validity.
1. Fog Collection Funnels Set Up Wrong
If the fog collection rate is wrong, the entire ASTM B117 salt spray test is off.
- Keep funnels level and at the same height as the test panels.
- Make sure the collection area is 80 cm² (as required by ASTM B117).
- Avoid placing funnels near doors, heaters, or walls where fog is not representative.
- Always record mL/h per 80 cm² and confirm it’s within the required 1.0–2.0 mL/h range.
2. Contaminated Salt Solution
Your 5% sodium chloride NaCl solution is the heart of the test. Bad solution = bad data.
- Use high‑purity NaCl (no anti-caking agents, no additives).
- Only use distilled or deionized water to avoid minerals and ions.
- Clean tanks, piping, and mixing containers regularly to prevent algae, rust, or sludge.
- Mix fresh solution at least as often as your internal procedure or customer requires.
3. Poor Chamber Sealing and Temperature Control
ASTM B117 neutral salt spray requires 35 °C ± 2 °C. Leaks kill stability.
- Check door gaskets and seals for cracks, hardening, or compression set.
- Look for visible fog leakage around lids, doors, and cable ports.
- Verify temperature with calibrated sensors at multiple points inside the chamber.
- If you see localized corrosion differences, suspect non-uniform fog distribution.
4. Wrong Specimen Support Materials
Support materials can quietly contaminate the test.
- Avoid steel, copper, zinc, or other metals that can corrode or react in the salt fog.
- Use inert supports (plastic, glass, or high‑grade non-reactive materials).
- Make sure supports don’t create galvanic couples with the specimen.
- Do not let parts touch each other; avoid stacking and shadowing.
5. Poor Cleaning, Handling, or Labeling of Samples
What you do before and after exposure is just as important as the exposure itself.
- Clean samples according to spec or ASTM guidance—no aggressive solvents unless specified.
- Wear clean gloves to avoid fingerprints and oils that change corrosion behavior.
- Use non-corroding labels or tags that won’t bleed, fall off, or react in salt spray.
- After testing, rinse gently, dry in controlled conditions, then evaluate without delay.
- Document everything: ID, orientation, position in the chamber, and any anomalies.
If you avoid these common failures, your ASTM B117 salt spray test results will be stable, credible, and trusted by customers—whether you’re qualifying coatings, benchmarking suppliers, or running daily QC in a global lab environment.
Sample ASTM B117 Test Report – What Should Be Included
A clean, complete ASTM B117 salt spray test report is non‑negotiable. Here’s what I always include so customers, auditors, and OEMs don’t push back.
1. Basic Test Identification
At the top of the report, lock in the basics:
- Standard: ASTM B117, revision (e.g. ASTM B117‑19)
- Test name: Neutral Salt Spray (NSS) corrosion resistance test
- Lab details: lab name, address, contact
- Chamber ID: model, serial number, location
- Test dates: start date/time, end date/time
- Work/order number: customer PO, internal job ID
This makes traceability easy when you’re comparing results across plants or regions.
2. Detailed Test Parameters
Next, spell out the actual salt fog testing conditions:
- Solution: 5 ± 1% sodium chloride (NaCl) by mass
- Water quality: distilled or deionized, conductivity if measured
- pH of solution: target 6.5–7.2, with recorded values and adjustment method
- Chamber temperature: 35 °C ± 2 °C (log actual range)
- Fog collection rate: mL/h per 80 cm² from collection funnel, min/max/average
- Air pressure: atomizing pressure during test (kPa or psi)
- Test duration: total hours of continuous salt spray exposure
Frequently Asked Questions About ASTM B117 Salt Spray Testing
How long is a typical ASTM B117 salt spray test in hours?
For the ASTM B117 salt spray test, there’s no fixed “standard” number of hours. The duration is always defined by the coating or customer spec. That said, this is what I usually see in real projects:
- Basic zinc plating: 24–96 h neutral salt spray (NSS)
- Industrial powder coatings: 240–500 h NSS for qualification
- High-performance / automotive systems: 720–1,000+ h NSS or more
I always remind customers: more hours ≠ direct extra years in service. Use the salt fog testing standard mainly for comparisons and quality control, not for exact life prediction.
Can I use distilled water instead of deionized water?
Yes, you can use distilled water in ASTM B117 as long as the quality is under control. The standard allows both distilled and deionized water, but what really matters is:
- Low conductivity and low contamination (minimal chlorides, sulfates, metals)
- Consistent water quality for every batch of 5% sodium chloride solution
- Regular checks and documentation in your ASTM B117 test report
In our Derui salt spray chambers, most global labs use deionized water as the safer default, and switch to distilled only when they know the source is clean and stable.
Is ASTM B117 still relevant in 2026–2026?
Yes, ASTM B117 is still very relevant. Even with modern cyclic corrosion testing (CCT) standards, most of my customers keep ASTM B117 for:
- Fast screening of new materials and coatings
- Routine QC in production lines
- Benchmarking against existing products and competitor data
For realistic service life, CCT methods (like GMW 14872 or OEM cyclic specs) are better. But for simple, repeatable, low-cost corrosion resistance testing, the ASTM B117 salt spray test is still a global workhorse.
What is the difference between NSS, AASS, and CASS?
These are three common salt spray test types:
- NSS (Neutral Salt Spray):
5% NaCl, pH ~6.5–7.2, 35 °C; this is the classic ASTM B117 neutral salt spray (NSS) used for many metals and coatings. - AASS (Acetic Acid Salt Spray):
Same base solution but acidified with acetic acid; more aggressive, often used for decorative coatings and certain plated finishes. - CASS (Copper-Accelerated Acetic Acid Salt Spray):
AASS with copper added; very severe, typically used for high-end decorative and nickel–chrome systems.
ASTM B117 focuses on NSS, while other standards define AASS and CASS in more detail.
Do Derui salt spray chambers support CCT as well as ASTM B117 NSS?
As a professional environmental test chamber manufacturer, our Derui salt spray chambers are built to run ASTM B117 NSS precisely, and we offer options for cyclic corrosion testing (CCT) as your lab grows.
- Standard units: Full compliance with ASTM B117 and ISO 9227 neutral salt spray (NSS), with tight 35 °C temperature control and verified fog rate.
- CCT upgrades: Programmable cycles (spray, dry, humidity, air purge), extra temperature and humidity control, and flexible profiles for OEM and automotive specs.
- Calibration support: We provide salt spray cabinet calibration, third-party validation, and documentation so you can show compliance to global customers.
This way, you can start with ASTM B117 NSS and scale up to CCT without changing your core chamber platform.
