Product Specification

Salt Spray Hours on Stainless Wire: What the Number Really Means

A salt spray figure is usually read as a service-life promise. It is not. It is a ranking of two materials under one fixed, continuous set of conditions, and the number is only meaningful when the grade, the surface finish and the test standard are quoted next to it.

This wire is annealed at 550-750 N/mm2 in 304 and 316L, supplied from 0.15 mm to 12 mm in bright annealed, bright drawn or pickled finish. Where a customer specifies a salt spray requirement, the grade, the finish and the acceptance criterion are agreed before the coil is drawn, because all three change the result.

The standard behind most numbers is neutral salt spray to ASTM B117 or ISO 9227 NSS: 5% sodium chloride solution, 35 C, continuous fog. Every hour of that test is one hour of permanent wetting, which almost no real installation ever sees.

Product Specifications

What the Test Actually Holds Constant

Fog, not cycles

The sample stays wet for the whole duration. Real service alternates wet and dry, and the drying phase is when the passive layer re-forms. A wire that survives 500 hours of continuous fog has demonstrated something stricter in one sense and less realistic in another.

One chloride concentration

5% sodium chloride is far above most atmospheric exposures and below a splash zone. Results cannot be scaled to a coastal distance, a road-salt route or a washdown chemical; they only rank materials against each other under that one condition.

The first visible defect ends the test

Whether the failure criterion is pitting, staining or red rust changes the reported hours by a large margin. Two suppliers quoting 300 hours can be measuring different events, which is why the criterion belongs in the specification.

Where the Hours Are Useful

Ranking two grades

Run 304 and 316L from the same surface finish through one test and the difference in hours is a genuine, repeatable signal, because molybdenum changes the pitting resistance of the same base structure.

Ranking two surface finishes

A pickled surface and a bright annealed surface of the same grade can differ noticeably, because residual scale and embedded iron become initiation sites. This is the comparison that most often explains a customer complaint.

Spotting a process problem

A lot that falls far below the hours of the same grade supplied last year is a signal about drawing lubricant, annealing atmosphere or contamination - not about the grade.

Where the Hours Are Not Useful

As a service life

No conversion exists from salt spray hours to years in a given environment. Anyone offering one is extrapolating from a single accelerated condition.

As a substitute for exposure data

Where a part is already in service, the field record from that site outweighs any laboratory number. Coastal distance, prevailing wind, cleaning chemicals and dwell time all sit outside the test.

Applications

Coastal and de-icing exposure

Grilles, ties and guards near salt water or road salt, where 316L is specified and the finish is controlled rather than left to the drawing default.

Food plant washdown

Frames and baskets cleaned with chlorinated or acidic agents, where grade and surface both decide how long the part stays free of pitting.

Marine and pool hardware

Fittings, lanyards and mesh in salt or chlorinated water, where 316L is the starting point and a smooth surface is part of the specification.

Product Advantages

• Grade and finish quoted together - a salt spray figure is meaningless without both, so both are stated on the offer.
• Test standard named - ASTM B117 or ISO 9227 NSS, with the conditions, rather than an unattributed hour count.
• Acceptance criterion agreed up front - pitting and staining give very different hours, so the criterion is fixed before testing.
• Surface controlled as a corrosion variable - scale, die lines and embedded iron are inspected, because they start pitting before the grade does.
• Honest grade boundaries - 304 for fresh water and normal atmosphere; 316L where chlorides, salt air or washdown chemicals are present.
• Full size range - 0.15-12 mm, so fine mesh and structural wire are tested and documented on the same basis.

Quality Control

Rod grade is verified by chemical or PMI check before drawing. Diameter is measured inline and at coil ends, tensile and elongation are tested per heat per ISO 6892-1, and surface is inspected for scale, die lines and iron contamination. Salt spray testing is carried out on request, with the standard, conditions and criterion recorded on the report.

Selection and Ordering Notes

1. Name the actual environment: salt air, road salt, chlorinated water, acid washdown or fresh water.
2. State the surface finish, since it moves the result more than most buyers expect.
3. If a salt spray figure is required, specify the standard and the failure criterion with it.
4. Give the bend radius and forming process, so the surface requirement is realistic at the bend.
5. Provide sizes and annual volume for a tolerance and packing review.

Send the grade, diameter, service environment and any corrosion test requirement for technical confirmation and quotation.