What Do 72-Hour and 96-Hour Salt Spray Ratings Really Mean?
Salt spray rating such as “72 h” or “96 h” is easy to read as a durability promise. It is not. A salt spray rating is a pass/fail result at a checkpoint, not a service life figure. This article explains what a connector salt spray test measures, how 72-hour and 96-hour ratings are judged, and how to choose a rating for coastal, automotive, or outdoor use.
What a 72- or 96-Hour Salt Spray Rating Means
A connector rated for 96 hours of salt spray met its acceptance criteria after 96 continuous hours in the chamber. It has not “failed” at hour 97; the test ended at a checkpoint agreed on in advance.
The test behind the rating
The sample runs in a continuous fog of 5 percent NaCl at 35°C (ASTM B117 or ISO 9227), then is evaluated on:
- Base-metal corrosion (visible rust or copper salts).
- Contact resistance change (four-wire method).
- Insulation resistance between circuits.
- Seal integrity, for waterproof connectors.
What the rating does not tell you
Salt spray testing has no acceleration factor: a 96-hour rating does not mean the connector survives 96 hours in a coastal environment. In service, temperature cycling, humidity, vibration, and road salt chemistry drive corrosion a static fog cannot reproduce. For where this test is required, in marine, automotive splash zones, and military equipment, see the article on connector testing in salt spray environments.
The Test Behind the Number: ASTM B117 and ISO 9227
Both standards describe the same neutral salt spray (NSS) procedure: 5 percent NaCl atomized into a fine fog at 35°C, pH 6.5 to 7.2. A datasheet that says “salt spray: 96 h” refers to this NSS test, not the AASS or CASS variants.
72-hour and 96-hour ratings come from the same test run longer; only exposure time changes. The longer run gives corrosion more time to nucleate and propagate through plating defects, which is why a part can pass 72 hours and fail 96.
| Exposure | Continuous NSS exposure | Typical expectation |
| 72 hours | Three days of salt fog | Contacts retain function; minor tin oxide is acceptable |
| 96 hours | Four days of salt fog, 33 percent longer | Base-metal corrosion stays within limits; contact resistance is the deciding check |
For the full standard list used in harness qualification, including IEC 60068-2-11, IEC 60068-2-52, and GB/T 2423.18, see the guide to the wire harness connector salt spray test according to standard.
How a Salt Spray Rating Is Judged: Pass/Fail Criteria
Two “96-hour rated” parts can differ if the suppliers used different acceptance criteria.
Visual corrosion rating
Corrosion is graded per ISO 10289 or ASTM D1654 from 0 to 10, based on the percentage of corroded area:
| Rating | Corroded area (% of surface) |
| 10 | 0 |
| 9 | Up to 0.1 |
| 5 to 8 | 0.1 to 2.5 |
| 0 to 4 | More than 2.5 |
Most connector specifications require a minimum rating of 9 after exposure: no base-metal corrosion beyond 0.1 percent of the surface. White or light gray oxide on tin is expected and acceptable; red rust on steel, or green copper salts on brass, means the plating has been breached.
Contact resistance is the real pass/fail
Appearance is secondary to function; what matters is the change in contact resistance, measured before and after exposure with a four-wire Kelvin setup. A typical limit is a maximum increase of 10 mΩ, or a 20 to 30 percent rise over the initial value.
Plating Is What Separates 72 Hours From 96 Hours
Salt spray resistance comes from the contact plating, not the housing; a 96-hour rating demands the plating system be specified for it.
| Contact plating | Typical behavior in neutral salt spray | Relative cost |
| Gold over nickel underplate | Excellent pore and creep corrosion resistance | High |
| Tin-nickel alloy | Very good; harder and more corrosion resistant than tin | Medium |
| Tin over nickel underplate | Good; oxide forms, contact stays conductive | Low to medium |
| Tin on brass or phosphor bronze | Acceptable for 72 to 96 hours in most designs | Low |
| Bare copper or brass | Rapid green or red corrosion; fails early | Lowest |
Tin plating is the workhorse for cost-sensitive connectors. During salt spray, tin forms a thin, self-limiting oxide that the mating terminal wipes through on engagement. That is why a tin-plated connector can hold contact resistance after 96 hours even when its surface darkens. Watch for plating porous enough that the brass or phosphor bronze base corrodes through.
Waterproof Connectors vs Standard Connectors in Salt Spray
In a standard wire-to-board header, salt fog reaches the contacts directly and the rating rests almost entirely on plating. In a waterproof connector, a sealing ring and IP-rated interface keep electrolyte off the contacts, so the rating depends on seal aging, wire wicking, and crevice corrosion at the housing interface.
For a design that combines moisture exposure with a standard 2.0 mm wire-to-board footprint, a sealed header such as the A2005-WR series is worth evaluating. The A2005-WR02 is a 2-pin, single-row, right-angle header with tin-plated brass or phosphor bronze contacts, a Nylon 66 UL94V-0 housing, 3 A at 250 V, and -25°C to 105°C operation. Sealing keeps salt fog off the contact interface, worth more than any plating upgrade on an unsealed part.
One detail to confirm in any report: mated or unmated test condition. Sealed connectors are usually qualified in the mated state, representative of service; an unmated test is harsher and a different specification.
How to Read a Salt Spray Test Report and Choose the Right Rating
Reading the report
A trustworthy report states its conditions explicitly. Check for:
- The standard cited (ASTM B117 or ISO 9227) and variant (NSS, AASS, or CASS).
- Chamber conditions: NaCl concentration, pH, temperature, fog rate.
- Sample preparation and mated or unmated test condition.
- Exposure duration and the evaluation criteria used.
- Corrosion rating numbers per ISO 10289 or ASTM D1654, not just “no corrosion observed,” with contact resistance data and photos.
A report that omits the standard, states a duration without conditions, or gives no rating numbers cannot be compared against another supplier’s.
Choosing a rating by environment
| Application environment | Suggested salt spray rating | Connector type |
| Coastal or offshore equipment | 96 hours minimum | Waterproof, gold or tin-nickel plating |
| Automotive underbody | 96 hours | Sealed connector, tin-nickel or tin over nickel |
| Vehicle interior | 48 to 72 hours | Standard connector, tin plating |
| Outdoor appliances and tools | 96 hours | Waterproof with sealing ring |
Two practical rules apply regardless of environment. Test production lots, not laboratory prototypes, since salt spray exposes plating thickness variation. And when 96 hours is required, get the plating specification, thickness included, in writing.
FAQ
No. Salt spray testing has no acceleration factor, so exposure time does not translate into field lifetime. The rating is a comparative pass/fail result, not a service life predictor.
The test conditions are identical; 96 hours is roughly 33 percent more time in the chamber, so it is a stricter checkpoint.
ASTM B117 and ISO 9227 are the common neutral salt spray (NSS) standards; IEC 60068-2-11 and IEC 60068-2-52 apply in automotive and harness qualification. Confirm which standard the supplier cited before comparing.
Usually not. Tin forms a self-limiting oxide in salt fog that the mating terminal wipes through on engagement. Failure is base-metal corrosion, red rust or green copper salts, or contact resistance beyond the limit.
Yes. Sealing keeps electrolyte off the contacts, but the seal ages, water wicks along the wire, and crevice corrosion can start at the housing interface. Waterproof parts face a different failure mode, not exemption.
Only when standards, chamber conditions, exposure duration and evaluation criteria are identical. Two “96-hour ratings” are comparable only if they use the same pass/fail methodology and corrosion rating numbers.
Need Connectors Meeting Specific Salt Spray Ratings?
If your drawing requires 72-hour or 96-hour salt spray testing, clarify the standard, acceptance criteria and mated/unmated condition in advance. Suppliers who perform salt spray qualification on production connectors can provide full test reports to verify ratings. Contact us for salt spray test reports and samples.
