What Salt Spray Tests Reveal for Solar Aluminum Profiles?
2026-10-26
A solar mounting engineer is reviewing supplier documents for a 50 MW coastal project. One supplier submits a salt spray report showing 1,000 hours with a rating of 9.5. Another submits a report showing 500 hours with a rating of 8.0. The procurement team asks which profile is better. The engineer explains that the two reports cannot be compared directly because the test conditions and the rating methods are different. The numbers alone do not answer the question. The engineer must look at the test standard, the rating scale, the sample preparation, and the anodizing thickness behind each result. This is what salt spray tests reveal for solar Aluminum Profiles. They reveal the consistency of the surface treatment process, not a simple pass or fail label.
1. Why Does a Solar Mounting Project Need a Salt Spray Test at All?
Solar mounting structures are designed for 25 years of outdoor exposure. In coastal areas, the chloride concentration in the air can exceed 200 mg per square meter per day. Chloride ions attack the passive oxide film on aluminum and initiate pitting corrosion. The pit grows through the wall of the profile and reduces the structural capacity. A salt spray test is the standard method for evaluating the resistance of the surface treatment to this attack. In our factory, we require a salt spray report for every batch of Aluminum Profiles used in coastal projects. Ningbo Gangtong Zheli Fasteners Co.,Ltd. has been supplying solar aluminum profiles for over 12 years.
The test is not a guarantee of 25-year life. It is a comparative tool. It shows whether the anodizing or coating process is capable of resisting chloride attack for a meaningful period under accelerated conditions. A profile that fails at 200 hours will not survive a coastal installation. A profile that passes 1,000 hours with a high rating is a reasonable candidate for further evaluation.
2. What Exactly Does the Salt Spray Chamber Simulate, and What Does It Not?
The salt spray chamber simulates a continuous chloride environment. The standard conditions are a 5 percent sodium chloride solution, a chamber temperature of 35°C, a neutral pH of 6.5 to 7.2, and a continuous fog. The test accelerates natural corrosion by a factor of 10 to 50, depending on the material and the environment. The table below shows the relationship between test duration and the corresponding exposure in different environments.
| Test duration (hours) | Typical rating (GB/T 6461) | Approximate equivalent in coastal environment | Typical application |
| 200 | 8.0 – 8.5 | 3 – 6 months | Inland or sheltered mounting |
| 500 | 8.5 – 9.0 | 1 – 2 years | General outdoor mounting |
| 1,000 | 9.0 – 9.5 | 3 – 5 years | Coastal mounting |
| 2,000 | 9.5 – 10.0 | 6 – 10 years | Severe coastal or offshore |
Test engineer's note: The equivalent exposure values in the table are approximate. The actual corrosion rate depends on the chloride deposition rate, the humidity, the temperature, and the surface orientation. A salt spray test does not simulate UV exposure, thermal cycling, or mechanical loading. It is a single-factor test. For a full evaluation of a solar Aluminum Profiles, the salt spray result should be combined with UV aging, thermal cycling, and mechanical load tests. Ningbo Gangtong Zheli Fasteners Co.,Ltd. provides a combined test report on request.
3. How Do You Read a Salt Spray Report Beyond the Pass or Fail Label?
A salt spray report contains more information than a single number. The engineer should check five items. The first is the test standard. The report should state whether the test was performed according to ASTM B117, ISO 9227, or GB/T 10125. The second is the test duration. The third is the rating method. The report should state whether the rating is based on ASTM D1654, GB/T 6461, or another scale. The fourth is the sample preparation. The report should describe whether the sample was scribed, whether the edges were protected, and how the surface was cleaned before the test. The fifth is the observation detail. The report should describe the type of corrosion (pitting, blistering, creep from the scribe) and the location. The table below shows the meaning of the GB/T 6461 rating scale.
| Rating | Corrosion area | Typical appearance | Suitability for coastal solar |
| 10 | No corrosion | No visible change | Excellent |
| 9.5 | < 0.1% | Pinpoint pits, not visible to naked eye | Very good |
| 9.0 | 0.1 – 0.25% | Small pits visible under magnification | Good |
| 8.0 | 0.5 – 1.0% | Visible pits on the surface | Marginal |
| 7.0 | 2.5 – 5.0% | Large pits and blistering | Not suitable |
In our factory, we review the salt spray report for every batch of Aluminum Profiles. We reject any batch that does not meet the project specification for test duration, rating, and observation detail. NGL provides the original test report from an accredited laboratory with each shipment.
4. Why Does the Same Alloy Grade Sometimes Show Different Salt Spray Results?
Two profiles made from the same 6063 alloy can show different salt spray results. The difference is caused by the surface treatment process. There are four variables. The first is the anodizing thickness. A 10 micron anodized layer provides less protection than a 20 micron layer. The second is the sealing quality. The anodized layer is porous and must be sealed to prevent chloride ingress. A poorly sealed layer will fail earlier. The third is the surface pretreatment. The extrusion surface must be etched and desmutted before anodizing to remove impurities. The fourth is the alloy composition. The silicon and iron content affect the uniformity of the anodic film. The table below shows the effect of anodizing thickness on salt spray performance.
| Anodizing thickness (µm) | Sealing method | Salt spray duration to rating 9.0 | Typical application |
| 10 | Cold seal | 200 – 300 hours | Indoor or sheltered |
| 15 | Cold seal | 400 – 600 hours | General outdoor |
| 20 | Hot seal | 800 – 1,000 hours | Coastal |
| 25 | Hot seal | 1,200 – 1,500 hours | Severe coastal |
In our factory, we specify a minimum anodizing thickness of 20 microns for coastal solar projects. We also require the anodizing supplier to provide a sealing quality test (acid dissolution test or admittance test) along with the salt spray report. Ningbo Gangtong Zheli Fasteners Co.,Ltd. audits the anodizing suppliers every year to verify the process consistency.
5. How Should a Project Specify Salt Spray Requirements That Are Both Meaningful and Verifiable?
A meaningful specification must include five items. The first is the test standard. The second is the test duration. The third is the required rating and the rating method. The fourth is the sampling location on the profile. The fifth is the acceptance criteria for the observation detail. The specification should not simply state "salt spray resistant" or "pass 500 hours" without the rating method and the observation detail. The table below shows an example of a well-written specification.
A well-written specification reads: "The Aluminum Profiles shall be tested according to ISO 9227 with a 5% NaCl neutral salt spray for 1,000 hours. The rating shall be determined according to GB/T 6461. The minimum rating shall be 9.0 with no pitting deeper than 0.1 mm. The samples shall be taken from the web surface of the profile at least 300 mm from the extrusion end. The test report shall include photographs of the samples before and after the test." This specification is verifiable and leaves no room for interpretation. In our factory, we help customers write this type of specification and we verify the test report against the specification before shipment.
Frequently Asked Questions About Salt Spray Tests for Solar Aluminum Profiles
Summary for PV Mounting Engineers and Procurement Teams
Salt spray tests reveal the resistance of solar Aluminum Profiles to chloride attack, but the result must be read correctly. The test standard, the duration, the rating method, the sample preparation, and the observation detail all matter. The same alloy grade can show different results depending on the anodizing thickness and the sealing quality. A meaningful specification states the test standard, the duration, the rating, the sampling location, and the observation criteria. The test result should be combined with anodizing thickness and sealing quality data to estimate the service life. Ningbo Gangtong Zheli Fasteners Co.,Ltd. has been supplying solar aluminum profiles for over 12 years and provides full salt spray verification support for our customers.
