For fasteners, brackets, and other metal hardware used in Australia and New Zealand, corrosion protection is always a key topic. Coastal environments, high UV, and long design lives all push engineers and purchasers to ask for “better coating” and “more hours in salt spray”. However, salt spray requirements are often written in very different ways, and not everyone is clear about what those numbers really represent.
This article looks at how salt spray tests are commonly used in the AU/NZ market, especially for fasteners and small metal parts. It explains what salt spray testing actually measures, typical hour levels requested for different coatings, and how to write clear, realistic specifications when you send RFQs to your suppliers.
1. What Is Salt Spray Testing and Why Is It Used?
Salt spray testing is a laboratory corrosion test where coated or uncoated specimens are exposed to a fine mist of salt solution at controlled temperature and humidity. The most widely used international standard is ISO 9227, which defines neutral salt spray and other variations for coated and uncoated metals. The test is simple, relatively quick, and widely available in testing labs.
In practice, salt spray testing is used to:
- Compare different coatings or surface preparation methods on the same substrate.
- Check production consistency for a well-established coating system.
- Screen for major problems such as pores, pinholes, or incomplete coverage.
In the AU/NZ market, purchasers often use salt spray hours as a convenient way to describe their expectations for fasteners, cold formed parts, and other hardware supplied into construction, infrastructure, and machinery projects.
2. What Salt Spray Tests Can and Cannot Tell You
Before looking at typical hour levels, it is important to remember the limitations of salt spray testing.
2.1 What salt spray tests tell you
Salt spray tests are useful for:
- Comparing different coatings: for example, basic zinc plating versus zinc flake coating on the same type of hex bolt.
- Finding obvious defects: pinholes, thin edges, or uncoated areas become visible as early corrosion spots.
- Quality control over time: when a coating system and test method are fixed, repeated salt spray tests can show whether new batches are consistent with previous ones.
2.2 What salt spray tests do not tell you
However, salt spray hours are not a direct prediction of service life:
- The test uses a continuous salt fog, which is very different from real conditions where parts may dry out between wet cycles.
- It does not simulate UV, temperature cycling, or real contaminants such as dirt or chemicals.
- It does not consider design factors such as crevices, drainage, or contact with other metals.
For long-life structures and infrastructure, AU/NZ designers rely on atmospheric corrosion categories and coating guidance in standards such as AS/NZS 2312 for structural steel, rather than only on salt spray hours. Salt spray is one small part of the overall picture.
3. Typical Salt Spray Requirements for Fasteners and Small Parts
While every project is different, certain patterns are common when buyers in the AU/NZ market ask for salt spray performance. The following values are typical examples, not hard rules. They should always be combined with a defined test method (for example ISO 9227 neutral salt spray) and clear failure criteria.
3.1 Electroplated zinc coatings
Electroplated zinc is commonly used on screws, bolts, nuts, and small stamped parts for indoor or mild outdoor environments. Common requests include:
- 24–72 hours to white corrosion and
- 96–240 hours to first red rust
on a neutral salt spray test, depending on zinc thickness and any passivation or topcoat used.
These levels are usually acceptable for indoor applications, sheltered outdoor locations, or components that are not directly exposed to marine atmospheres. When purchasers in AU/NZ specify “standard zinc plated fasteners”, they often assume this range unless higher performance is clearly requested.
3.2 Hot dip galvanized fasteners and parts
Hot dip galvanizing provides a thick zinc coating with excellent performance in many AU/NZ environments. For structural steel, designers typically follow corrosion guidance such as AS/NZS 2312 and related documents that classify environments (e.g. C2, C3, C4) and define protective systems, rather than specifying salt spray hours only.
For fasteners and small parts, some buyers still request a simple salt spray check, but it is more common to focus on:
- Coating thickness and visual standards for hot dip galvanizing.
- Appropriate steel grade and fastener design for galvanizing.
- Compatibility between galvanized fasteners and galvanized structural members.
Because hot dip galvanizing is a sacrificial coating designed for long-term outdoor use, salt spray hours alone are not the best way to judge its performance. In many cases, project specifications refer to hot dip galvanizing standards and durability guides from local galvanizers’ associations instead of salt spray results.
3.3 Zinc flake and other high-performance coatings
Zinc flake and similar high-performance coatings are widely used for automotive parts, structural fasteners, and coastal applications where traditional zinc plating is not enough, especially when hydrogen embrittlement risk needs to be controlled for high-strength fasteners.
Typical requirements in AU/NZ projects include:
- 480 hours to first red rust, or
- 720–1,000+ hours to red rust for premium systems or duplex coatings.
These higher hour levels are usually connected with specific coating brands or processes, and purchasers may refer to the coating supplier’s performance data when defining requirements.
3.4 Painted or duplex systems
For structural components and fasteners with paint or duplex (galvanized + paint) systems, designers often refer to environmental categories and durability expectations rather than a single salt spray number. Salt spray tests may be used as part of coating qualification, but the key parameters are:
- Correct surface preparation.
- Compatible primer and topcoat system.
- Required durability class in the project (for example “high durability, C4 coastal environment”).
In these cases, fastener purchasers usually align with the coating designer’s specification instead of creating independent salt spray requirements.
4. Salt Spray in the Context of AU/NZ Corrosion Standards
Australia and New Zealand have a strong framework of standards and industry guidelines for corrosion protection. These documents focus on environment categories and acceptable protective systems rather than only laboratory tests.
For example, guides to the protection of structural steel against atmospheric corrosion classify typical environments such as inland, industrial, or marine and recommend suitable coating systems for each category. Galvanizers’ associations in both countries also publish practical design and durability guides for hot dip galvanized steel, including typical service lives and maintenance recommendations.
When AU/NZ engineers and asset owners evaluate fasteners, they often look for:
- Whether the fastener coating system is compatible with the structural coating system.
- Whether the fastener material and coating match the same corrosion category as the connected steelwork.
- Whether small parts like bolts, nuts, and washers have similar or better durability than the main structure.
Salt spray hours can support this assessment, but they are usually only one check among several.
5. How to Specify Salt Spray Requirements in RFQs
From a purchasing point of view, the most important step is to write clear, realistic salt spray requirements that match the real application and do not create unnecessary cost or confusion. Below is a practical checklist you can use when sending RFQs for coated fasteners and metal parts.
5.1 Define the test method and sample preparation
Always state:
- The test standard, for example ISO 9227 neutral salt spray.
- The sample type, such as finished bolts with nuts and washers assembled, or flat test coupons coated with the same process.
- Whether any post-treatment or sealing must be completed before testing.
If you only state “500 hours salt spray”, different suppliers may use different methods and criteria. A clear method avoids arguments later.
5.2 Specify performance criteria
Performance is not only a number of hours. Include:
- The required hours to first appearance of white corrosion and/or red rust.
- Which areas are judged (for example full surface or only flat areas, excluding edges and stamped marks).
- How many samples must pass, and whether any localized defects are allowed.
For example, a typical requirement might be: “ISO 9227 neutral salt spray test, 480 hours to first red rust on significant surfaces of bolts; slight white corrosion accepted.”
5.3 Link salt spray requirements to the real environment
Provide information about:
- Whether the parts will be used indoors, outdoors, coastal, or industrial.
- Expected design life and maintenance strategy.
- Whether the parts are part of structural steelwork, roofing, mechanical equipment, or other systems.
This helps your supplier check whether your requested salt spray level is realistic and aligned with AU/NZ corrosion categories. In some cases, they may suggest a slightly different coating system that better matches the environment, even if the salt spray hours are similar.
5.4 Ask for coating recommendations and documentation
Experienced suppliers and coating applicators can often propose multiple options at different cost and performance levels. When sending your RFQ, you can ask:
- Which coating systems they commonly use for AU/NZ coastal or industrial projects.
- Typical salt spray performance for each system.
- What kind of inspection and test reports they can provide.
This open discussion usually leads to a more cost-effective and reliable solution than simply demanding a very high salt spray hour number without context.
6. Salt Spray Requirements for Different Product Types
Different product families have different typical expectations in the AU/NZ market. Below are some examples you may encounter when purchasing.
6.1 Fasteners and fixing hardware
For general-purpose bolts, nuts, washers, and screws used in construction and machinery, common combinations include:
- Zinc plated fasteners for indoor and mild outdoor: 96–240 hours to red rust, depending on coating type and thickness.
- Zinc flake coated high-strength fasteners for structural joints or automotive applications: 480–1,000+ hours to red rust.
- Hot dip galvanized fasteners matching galvanized structural steel: focus on coating thickness and adherence to established hot dip galvanizing standards, with salt spray used only as a secondary check.
You can explore typical product ranges at
https://linkworldfast.com/product-category/bolts-nuts-washers/
and
https://linkworldfast.com/product-category/screws/
6.2 Brackets, plates, and fabricated parts
For stamped and welded brackets, plates, and other fabricated parts, requirements are usually aligned with the surrounding steelwork. For example:
- In a rural or light industrial environment, a zinc-rich primer plus topcoat system may be sufficient.
- In a coastal or marine environment, hot dip galvanizing or duplex systems are more common.
In RFQs, it is good practice to state whether these parts must match the same corrosion category as the supporting structure and whether they will be painted on site or only coated at the factory.
7. Working With Suppliers on Salt Spray and Corrosion Performance
For exporters and local distributors supplying into the AU/NZ market, salt spray performance is both a technical and a commercial topic. A good supply partner will not only process your drawings but also help you match coating systems, salt spray expectations, and packaging to the needs of the final project.
When you discuss with your supplier, you can:
- Share drawings and environment descriptions rather than only salt spray hours.
- Ask for alternative coating options that might reduce cost or lead time while still meeting AU/NZ corrosion expectations.
- Confirm what in-house inspection the supplier can perform, such as coating thickness measurement, salt spray pre-tests, and visual checks.
A supplier with its own cold forming capability, inspection room, and cooperation with different coating lines can usually support customized coatings, combined shipments of fasteners and other metal parts, and flexible small packing for direct delivery to site warehouses.
For an overview of available product families and services, you can visit
https://linkworldfast.com/products/
and learn more at
https://linkworldfast.com/about-us/
8. Conclusion: Using Salt Spray Requirements Effectively in AU/NZ Projects
Salt spray tests are a useful tool in the AU/NZ market, but their value depends on how they are specified and interpreted. “Hours in salt spray” should not be treated as a simple lifetime guarantee. Instead, salt spray performance should be:
- Linked to a clear test method and failure criterion.
- Consistent with the coating system and environment category defined for the project.
- Used as one part of a broader strategy that includes correct material selection, coating design, and good detailing.
When you send RFQs for fasteners, cold formed parts, and other hardware to the AU/NZ market, try to connect your salt spray requirements with real service conditions and recognized corrosion guidance. This approach will help you receive realistic proposals, avoid over-specification, and achieve durable performance in the field.
If you are planning a project that needs fasteners, screws, rigging items, or other customized metal parts with defined salt spray performance, you are welcome to browse
https://linkworldfast.com/
For detailed product selection and mixed hardware lists, you can explore
https://linkworldfast.com/products/
When you are ready to discuss drawings, coating requirements, and shipment plans, you can send your inquiry through
https://linkworldfast.com/contact/