How can the corrosion resistance of electroplated layers or coatings on hardware structural components be verified? The most widely accepted method is the salt spray test report;
it is almost universally recognized for export orders, project acceptance, and quality system audits.
This article explains where to get such a report, which standards apply, and the general process and costs involved.
1.
Select the Right Test Type and Standard
Salt spray tests are categorized by the corrosive environment: Neutral Salt Spray (NSS)—using a 5% sodium chloride solution and continuous spraying at 35°C—is the most common method, used to evaluate the corrosion resistance of electro-galvanized, nickel-plated, and powder-coated parts. Acetic Acid Salt Spray (AASS) and Copper-Accelerated Acetic Acid Salt Spray (CASS) offer higher acceleration rates and are used for chrome plating and decorative coatings.
The standard applied depends on the market: GB/T 10125 (covering the full NSS/AASS/CASS series) is used for the domestic market, while ISO 9227 or ASTM B117 is used for international orders.
A common specification found in orders is “48 hours of neutral salt spray with no red rust,” meaning there are no corrosion products from the base material on the surface after 48 hours of NSS testing.
2.
Where to Get It Done: Find a Qualified Third-Party Laboratory
Salt spray reports must be issued by third-party testing agencies holding CMA and/or CNAS accreditation. As long as the scope of accreditation (listed in the qualification annex) covers GB/T 10125, ISO 9227, or ASTM B117, the agency is qualified to perform the test.
Options include: national comprehensive testing organizations (e.g., CTI, GRGT, Sinosteel National Testing Center, SGS, etc., with branches in major cities), local specialized testing agencies (provincial/municipal quality inspection institutes), and industry-specific laboratories (e.g., the Architectural Hardware Quality Inspection Center).
When selecting a provider, verify that the laboratory’s accreditation scope (the appendix to the certificate) covers the relevant standards;
for export reports, ensure the inclusion of CNAS/ILAC mutual recognition marks.
III. Application Process, Timeline, and Costs
Process: Telephone or online consultation (clarify standards, duration, and pass/fail criteria) → Sample submission (quantities and dimensions per lab requirements; typically 2–3 pieces per coating type, plus spares for re-testing) → Quote confirmation and contract signing → Laboratory testing → Report issuance.
Regarding the timeline: the test duration itself varies (24, 48, 72, or 96 hours, etc.); standard reports are issued in 1–3 days, with a total turnaround time of about one week including testing. Costs are calculated per hour or per project; base prices range from tens to hundreds of yuan per piece, depending on the test type, duration, and whether expedited service is required.
IV.
How to Read and Use the Report
A salt spray test report should include: the standard and version applied, test conditions (salt solution concentration, temperature, duration), sample description (material and coating), test results (time of corrosion onset, corrosion rating), and the final conclusion.
Regarding usage: CMA reports are used for domestic factory audits and tenders, while CNAS/ILAC mutual recognition reports are used for export orders. Some clients also require the report to be accompanied by a coating thickness test (e.g., GB/T 6462) to provide dual evidence of “coating thickness” and “corrosion resistance duration.”
V. Three Key Reminders
- Clearly define test conditions: Factors such as salt spray duration, the specific standard version, and the presence of scribing (cross-hatch testing) significantly impact results; always confirm these details with the client and document them in writing when commissioning the test.
- Align reports with specific batches: A salt spray report applies only to the specific batch submitted for testing; for bulk orders, schedule testing based on plating batches, and re-test whenever the product’s surface treatment process changes.
- Beware of cheap “rubber-stamp reports”: Reports offered at prices far below market rates that do not require sample submission are highly likely to be fraudulent. Tendering parties and clients can verify report numbers via the State Administration for Market Regulation’s inspection and testing report inquiry platform;
falsification will directly jeopardize bidding eligibility and client trust.
Industry experts recommend incorporating both salt spray testing and coating thickness testing into the supplier’s factory inspection protocols: conduct routine self-inspections on sampled batches of plated parts and periodically submit samples to third parties for verification.
While the report serves as a “report card” for the client, consistent internal self-inspection is the fundamental practice that ensures the validity of those results.
