What is Salt Spray Testing

Salt spray testing is a corrosion resistance test used to evaluate how well materials, surface coatings, or finishes can withstand oxidative degradation when exposed to a simulated saline environment. This accelerated laboratory test recreates harsh conditions that products may face during storage, transportation, or end use, particularly in humid, coastal, or industrial environments.

By placing test samples in a controlled chamber where a fine saltwater mist is continuously sprayed, manufacturers and quality engineers can observe the onset and progression of corrosion over time. The results provide valuable data on the protective quality of coatings, metal substrates, or composite layers, supporting key decisions in product development, quality assurance, and compliance testing.

Salt spray testing is especially common in industries where durability and corrosion resistance are critical such as automotive, aerospace, hardware, electronics, and marine equipment manufacturing.

Introduction to Salt Spray Testing in Corrosion Control

Evaluating Corrosion Resistance with Salt Spray Testing

The primary purpose of salt spray testing is to evaluate a material or product’s resistance to rust, blistering, pitting, and degradation caused by salt-induced oxidation. It helps engineers determine:

How effectively a coating protects the base material
Whether a metal finish meets required durability standards
How quickly corrosion begins under specific environmental stress

Because of its repeatability and efficiency, salt spray testing has become a routine part of pre-shipment quality control, supplier audits, and certification requirements.

Salt Spray Testing in Global Manufacturing Standards

Despite its limitations in predicting exact real-world performance, salt spray testing continues to be widely used due to several key advantages:

Speed: Accelerates corrosion to produce results in days, not years
Standardization: Based on internationally recognized protocols (ASTM, ISO, JIS)
Cost-effectiveness: Less expensive than natural weathering or cyclic corrosion testing
Comparability: Useful for comparing multiple materials or coatings under identical conditions

Its ability to deliver repeatable, comparative data has kept it relevant in modern quality assurance workflows.

Common Materials Used for Salt Spray Testing

Salt spray testing is commonly applied to:

Metals: steel, aluminum, copper alloys, zinc alloys
Surface coatings: powder coatings, electroplating (e.g., zinc, nickel, chrome)
Paints and varnishes: organic or hybrid coatings
Composite materials: automotive trims, fasteners, and housing components

It is especially valuable for finished products intended for outdoor, industrial, or marine environments, where surface corrosion can directly impact safety, performance, or brand reputation.

Understanding ASTM B117 and Global Testing Standards

Overview of ASTM B117 Methodology

The most widely recognized standard for salt spray testing is ASTM B117, developed by ASTM International. First published in 1939 and continually refined since, this method specifies procedures for:

Preparing the salt solution (usually 5% NaCl by weight in distilled water)
Maintaining a chamber temperature of 35 ± 2°C (95°F)
Ensuring a consistent pH level between 6.5 and 7.2
Delivering a salt fog at a collection rate of 1.0–2.0 mL/hour on a horizontal surface

Specimens are positioned at a 15–30° angle from vertical, and test durations vary based on the expected corrosion resistance, typically 24, 96, 240, or even 1000 hours depending on the specification.

ASTM B117 does not define pass/fail criteria. Instead, it provides a controlled method by which users can generate comparable corrosion behavior data.

Key Parameters for Reliable Salt Spray Testing

Proper execution of a salt spray test depends on strict control over several variables:

Temperature: The chamber must be maintained at 35°C to replicate a warm, humid environment conducive to corrosion.
Salt concentration: The most common solution is 5% NaCl by weight.
pH level: Should remain neutral, between 6.5 and 7.2. Deviations can distort corrosion outcomes.
Spray rate: Must be monitored regularly using collection funnels to ensure consistent coverage.
Test duration: Varies by requirement but must be planned in advance and consistently followed.

These controls are vital to ensuring repeatable and meaningful test results that align with international norms.

Other International Standards: ISO 9227, JIS Z 2371

While ASTM B117 is dominant in the United States and many global sourcing chains, there are other relevant standards that are often required by regional regulations or buyer expectations:

ISO 9227: The European equivalent standard, widely accepted in the EU, especially for automotive and industrial coatings. Offers neutral salt spray (NSS), acetic acid (AASS), and copper-accelerated (CASS) variations.
JIS Z 2371: The Japanese salt spray test standard, widely used in Japanese manufacturing, with similar parameters to ASTM B117 but differing slightly in equipment and validation protocols.

When sourcing internationally or dealing with region-specific compliance needs, it’s essential to confirm which standard applies to your product line.

Salt Spray Testing Across Key Industries

1. Automotive

Used to test body panels, brake parts, fasteners, and coated underbody parts—especially in regions using road salt.

2. Electronics and Appliances

Validates protection for enclosures, metal brackets, and connectors in high-humidity or coastal settings.

3. Hardware and Tools

Used for product qualification of locks, fasteners, hinges, and hand tools, where corrosion directly impacts function.

4. Construction Materials

Supports compliance in structural joints, fencing, fasteners, and prefabricated metal components for marine or industrial zones.

5. Surface Treatment & Plating Industry

Validates durability of electroplated or galvanized finishes for batch consistency and claims verification.

Use in Pre-Shipment Inspection, Supplier Qualification, and Warranty Validation

For international buyers and quality control teams, salt spray testing supports several critical checkpoints in the sourcing and delivery process:

Pre-Shipment Inspection (PSI): Ensures that corrosion protection meets contractual specifications before goods leave the factory.
Supplier Qualification: Verifies a manufacturer’s capability to produce parts or components that meet long-term durability requirements.
Warranty Validation: Documents the corrosion resistance level claimed by the supplier or brand, supporting after-sales assurance and reducing product return disputes.

Testing is typically coordinated with third-party laboratories or inspection agencies, especially when transparency or impartiality is required.

Role in Regulatory Compliance and Product Claims

In many markets, salt spray testing is required to comply with industry regulations, procurement standards, or buyer specifications. For example:

ISO-certified quality systems often mandate corrosion testing for coated parts.
Government and military contracts frequently include salt spray criteria in technical documentation.
Product labeling such as “rust-resistant,” “marine-grade,” or “saltwater safe” must be substantiated by credible test results.

Failing to perform proper corrosion testing can lead to compliance failures, warranty costs, and brand reputation damage, especially in sectors with safety-critical applications.

Ensure your coatings and metals withstand real-world conditions. Salt spray testing provides a measurable benchmark for corrosion resistance and quality assurance. To integrate it into your inspection or QA process, work with a lab or third-party inspection provider experienced in international standards.

Need help verifying your product’s corrosion durability? ECQA offers lab coordination and pre-shipment inspections that include salt spray testing support. Contact us today to schedule your quality consultation.