Accelerated Aging Test for Cold Chamber Handles

Corrosion is the first enemy of all products and materials made of metal.

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But not all products are created equal. Some, due to their context and function, are more exposed to corrosion and require more urgent prevention. This is the case with cold storage components.

In the following article, we'll explore how corrosion occurs and how to combat it , and why it's vitally important to perform climate tests on cold storage components.

Corrosion and Accelerated Aging Test

Corrosion is an electrochemical process that affects all metals and their alloys. When exposed to atmospheric agents, primarily humidity and water vapor, metals tend to oxidize, forming the characteristic rust that worsens their physical properties until they crack or break.

Over the years, scientists and researchers have developed alloys and materials capable of resisting this process for a very long time. These materials are then subjected to test accelerated aging to study their resistance to corrosion in natural environments and evaluate their compliance with international standards.

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Cold Chamber Components

Not all metallic materials are exposed to corrosive agents to the same extent, nor does their corrosion have the same consequences for their use.

The components of cold storage chambers, for example, must ensure high resistance to corrosion due to the particular environment for which they are intended and the essential function they perform.

By components we mean all the tools needed to close, open, and insulate a cold chamber, therefore:

• Handles
• Hinges
• Compensation valves
• Sliding systems

Due to their essential functions, each of these components must be built according to certain international standards that guarantee a certain level of corrosion resistance.

International Standards for Salt Spray Testing

Accelerated corrosion ageing tests are regulated by the international standard EN ISO 9227:2017.

The standard provides for the salt spray test as a test to investigate the effects of corrosion on a material in artificial environments, i.e. inside a climatic chamber.

In the salt spray test, the climatic chamber is equipped with diffusers that spray the material being tested with a salt solution capable of causing the corrosive phenomenon.

We talked about it in detail here.

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The FDM Salt Spray Climatic Chamber

FDM climatic chambers are the ideal tool for conducting salt spray tests on cold chamber components and on all materials that need to comply with EN ISO 9227:2017 standards.

In each FDM climatic chamber, the relative humidity and temperature parameters necessary to conduct each accelerated aging test can be altered and can be equipped with salt spray diffusers to carry out the aforementioned test.

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Reference Standards

• UNI EN ISO 9227:2017 — Corrosion tests in artificial atmospheres – Salt spray tests (NSS, AASS, CASS), international reference for all accelerated corrosion tests.
• ISO 16701:2015 — Paints and varnishes – Corrosion testing by alternate immersion in salt solution, cyclic test for coatings.
• ISO 11997-1:2017 — Determination of resistance to cyclic corrosion conditions – Part 1: Wet (salt fog)/dry/humidity.
• ASTM B117-19 — Standard Practice for Operating Salt Spray (Fog) Apparatus, a historic American standard still in force.
• EN 1670:2007 — Window and door hardware – Corrosion resistance, classes 0-5 with 24 to 480-hour salt spray test.
• ISO 12944-6:2018 — Paints and varnishes – Corrosion protection of steel structures – Part 6: Laboratory performance test methods.

Authoritative Sources

• ISO – International Organization for Standardization. International standards body that manages the ISO 9227, 11997, and 16701 series for corrosion testing.
• ASTM International. American body that maintains ASTM B117, the oldest salt spray standard (1939).
• AMPP (formerly NACE International). Global association of corrosion professionals, publishes guidelines and best practices.
• UNI – Italian Standards Organization. Distributes EN/ISO standards applicable to the Italian refrigerator and refrigeration industry.

Frequently Asked Questions About Cold Storage Aging Tests

How many hours of salt spray does a cold storage door handle require?

Durability depends on the exposure class and the constituent material. For coated AISI 304 stainless steel handles , the typical test is 500-1000 hours NSS according to ISO 9227; for marine-grade AISI 316L, the test range is 1500-2000 hours. For anodized or powder-coated aluminum alloy components, 240-480 hours CASS (more aggressive, with CuCl ₂ ) is often used. The EN 1670:2007 standard classifies the resistance of hardware into 5 classes: Class 5 = 480 hours NSS with no visible defects (rust, blistering, delamination). The acceptance criteria follow ISO 10289:1999 with a rating classification of 10 (perfect) to 0 (completely corroded). For industrial cold chambers exposed to high humidity and sanitization with halogenated solutions, Class 5 with an additional margin is recommended.

What is the difference between NSS, AASS and CASS?

ISO 9227 defines three methods with increasing aggressiveness. NSS (Neutral Salt Spray): 5% NaCl solution, pH 6.5-7.2, temperature 35 ± 2 °C — general method for most metals and coatings. AASS (Acetic Acid Salt Spray): 5% NaCl + acetic acid, pH 3.1-3.3, 35 °C — used for decorative Cu-Ni-Cr coatings and anodic oxides. CASS (Copper-Accelerated Acetic Acid Salt Spray): 5% NaCl + acetic acid + CuCl₂, pH 3.1-3.3, 50 °C — the most aggressive, for severe accelerated tests. The acceleration factor between NSS and CASS is typically 3-5x on corrosive phenomena. The choice depends on the material: for galvanized carbon steel, NSS is used; for galvanized decorations, AASS or CASS; For marine environments, ISO 11997-1 cyclic tests are preferred, which alternate more realistic wet/dry phases.

Why are cyclic tests increasingly replacing continuous salt spray?

Comparative studies have shown that continuous salt spray (NSS) does not faithfully reproduce real corrosion, which in a natural environment alternates between dry, wet, and depositional phases. Cyclic tests according to ISO 11997-1 and ISO 16701 alternate: salt spray phase (35°C/saturation/2 h) → dry phase (50-80°C/5-50% RH/4-8 h) → wet phase (30-45°C/90-99% RH/2-4 h). This cyclicity triggers real-world mechanisms such as pitting, crevice corrosion, and efflorescence that continuous spray masks. The correlation with outdoor exposure is 3-5 times more accurate. For cold storage handles exposed to periodic sanitization with disinfectant solutions and alternating humidity cycles, the cyclic tests ASTM G85 Annex A5 (Prohesion) and ISO 11997-1 Cycle B are considered more predictive. However, ISO 9227 remains the reference standard for production quality control.

How is a salt spray chamber qualified according to ISO 9227?

The chamber must guarantee strictly controlled parameters: temperature 35 ± 2 °C (NSS/AASS) or 50 ± 2 °C (CASS), atomization pressure 0.7-1.4 bar, deposition rate 1.5 ± 0.5 ml/h per 80 cm² measured with vertical collectors, NaCl concentration 50 ± 5 g/l, controlled pH. Annual qualification includes: calibration of thermometers with uncertainty ≤ 0.3 °C; verification of deposition rate with ISO 9227 Annex A collectors; pH measurement with a calibrated electrode (buffer 4.01 and 7.00); droplet count and spatial distribution. SAE 1008 steel (not plated) must show a weight loss of 70 ± 20 g/m² in 48 hours NSS as a confirmatory test. The chamber must be made of resistant material (reinforced PVC, fiberglass), with an air saturation system and calibrated solution heating. The T/RH are not directly exposed to the jet to avoid drift.