Photovoltaic Module Ammonia Corrosion Testing: IEC 62716 Methods, Samples, and Applications

Photovoltaic (PV) module ammonia corrosion testing evaluates how solar modules withstand the ammonia-rich atmospheres typical of livestock farms, greenhouses, and industrial sites. Conducted in accordance with IEC 62716 by accredited third-party laboratories, this accelerated environmental test verifies electrical performance, insulation safety, and material integrity after prolonged ammonia exposure. This article explains the test principle, sample requirements, procedures, pass criteria, and typical applications of ammonia corrosion testing for PV modules.

Technical Overview

Ammonia (NH3) is one of the most chemically aggressive airborne contaminants that a photovoltaic module can encounter during field service. Elevated ammonia concentrations occur in and around livestock and poultry buildings, manure storage areas, fertilizer manufacturing plants, industrial refrigeration facilities that use ammonia as a refrigerant, and wastewater treatment sites. Concentrations inside poorly ventilated animal housing can persistently reach the tens-of-ppm level, exposing rooftop or nearby PV installations for the entire service life of the system.

When ammonia dissolves in the thin moisture film that forms on a module surface under humid conditions, it creates a mildly alkaline electrolyte. This electrolyte attacks many of the materials used in conventional module construction, including silver metallization on solar cells, copper ribbon and solder joints, tin-plated conductors, junction box contacts and terminals, metallic frame hardware, and certain polymeric encapsulants. Ammonia can also react with acetic acid released by hydrolyzing ethylene-vinyl acetate (EVA) encapsulant, forming ammonium acetate, which further accelerates electrochemical corrosion of cell metallization and interconnects. The visible and measurable consequences include metallization discoloration, corroded busbars and ribbons, encapsulant yellowing, loss of adhesion, delamination, and degradation of maximum power output.

IEC 62716, "Photovoltaic (PV) modules – Ammonia corrosion testing," defines the internationally recognized laboratory method for assessing a module's resistance to this environment (adopted in Europe as EN IEC 62716). The test is applied as an environment-specific supplement to the baseline IEC 61215 design qualification and IEC 61730 safety assessment sequences, in the same way that salt mist corrosion testing based on IEC 60068-2-52 is applied for coastal installations. Testing is performed in specialized corrosion chambers operated by ISO/IEC 17025-accredited third-party laboratories.

Testing Samples

Full-Scale Production Modules

The primary test object is a complete, production-representative module identical in materials, layout, lamination, framing, edge sealing, junction box, cables, and connectors to the product intended for the market. Full-scale samples are required because ammonia attack is strongly influenced by edge construction, framing details, and junction box sealing, which cannot be evaluated on small coupons alone. The standard specifies a minimum number of identical modules per test campaign, commonly two, so that results can be cross-checked.

Mini-Modules and Material Coupons

For research and development screening, laboratories also test mini-modules, laminates without frames, and individual material coupons such as encapsulant sheets, backsheet films, ribbons, and junction box components. These smaller samples are useful for rapid comparison of encapsulant chemistries, edge seal designs, and corrosion-resistant coatings, although results on coupons are considered indicative rather than certification-relevant.

Sample Preparation and Initial Characterization

Before exposure, all samples are cleaned, conditioned, and fully characterized to establish baseline data. Typical initial measurements include visual inspection, current-voltage characteristic measurement at Standard Test Conditions (1000 W/m2, 25 °C cell temperature, AM 1.5G spectrum per IEC 60904-1 and IEC 60904-3), electroluminescence imaging, and the insulation resistance and wet leakage current tests specified in the IEC 61215-2 and IEC 61730-2 procedures.

Testing Items

The evaluation covers all performance, safety, and appearance attributes that ammonia exposure can degrade. The principal testing items are:

• Visual inspection for corrosion of cell fingers and busbars, ribbon and solder joint attack, frame and fastener corrosion, junction box degradation, encapsulant yellowing or browning, bubbles, and delamination.
• Maximum power determination (Pmax) and analysis of short-circuit current, open-circuit voltage, and fill factor, with calculation of power degradation relative to initial values.
• Electroluminescence (EL) imaging to reveal metallization corrosion, interrupted interconnects, and micro-cracks that are invisible to the naked eye.
• Insulation resistance testing to confirm dielectric integrity after corrosion exposure.
• Wet leakage current testing to verify that the module remains safe when its surface is wet and contaminated.
• Optional diagnostic items requested by clients, including infrared thermography, peel and adhesion testing of laminate interfaces, yellowness index measurement of encapsulants, and cross-sectional microscopy of corroded metallization.

Testing Methods

Test Apparatus and Exposure Conditions

Testing is carried out in a dedicated environmental chamber fitted with a controlled ammonia dosing system, gas-tight construction, and an exhaust neutralization stage, typically an acid scrubber, so that spent atmosphere is rendered harmless before release. Under IEC 62716, modules are exposed to a continuous atmosphere containing approximately 30 ppm ammonia at a chamber temperature of about 60 °C and a relative humidity of about 70% for four weeks (approximately 672 hours). These conditions accelerate the slow chemical attack seen on livestock buildings into a practical laboratory timescale while remaining representative of real agricultural service environments. Ammonia concentration, temperature, and humidity are monitored continuously with calibrated gas analyzers and sensors, and the recorded data form part of the test report.

Test Procedure

The general sequence applied by accredited third-party laboratories is as follows:

• Perform complete initial characterization: visual inspection, EL imaging, STC power measurement, insulation resistance, and wet leakage current tests.
• Mount the module in the chamber in the orientation required by the standard, with adequate spacing around the sample for uniform atmosphere circulation.
• Ramp and stabilize the chamber at the specified temperature, humidity, and ammonia concentration setpoints.
• Maintain the exposure continuously for the specified duration, with logged monitoring of all parameters and periodic verification of the ammonia feed.
• After exposure, remove the module, allow a defined recovery period, and repeat all initial electrical, imaging, and safety measurements under identical conditions.
• Compare pre- and post-test results, document all findings photographically, and evaluate the module against the acceptance criteria.

Acceptance Criteria

A module is considered to have passed the ammonia corrosion test when it shows no major visual defects as defined in the IEC 61215 inspection criteria, such as corrosion that could impair function or safety, extensive delamination, or significant encapsulant discoloration; when the insulation resistance and wet leakage current tests are passed; and when power degradation remains within the limit defined by the applicable test protocol, typically a small percentage loss consistent with IEC 61215-based judgment. The final pass/fail determination is documented in a formal laboratory test report.

Safety and Quality Assurance

Because ammonia is toxic and irritating even at low concentrations, testing facilities employ gas detection and alarm systems, forced ventilation, interlocked chambers, personnel protective equipment, and scrubbed exhaust systems. Sensor calibration, chamber verification, and traceable measurement equipment ensure that results are reproducible and defensible for certification purposes.

Applications

Ammonia corrosion testing supports a wide range of commercial and technical objectives:

• Product certification and market differentiation for modules marketed as suitable for installation on livestock, poultry, and dairy buildings, where buyers and certification bodies increasingly demand documented ammonia resistance.
• Project qualification for solar plants planned near fertilizer plants, chemical parks, ammonia-based refrigeration warehouses, and wastewater treatment facilities.
• Research and development of corrosion-resistant module designs, including polyolefin (POE) encapsulants, glass-glass laminates, advanced edge seals, protective metallization coatings, and sealed junction boxes.
• Failure analysis of field-returned modules from agricultural installations, helping manufacturers identify whether observed degradation is ammonia-related.
• Combined-stress research protocols in which ammonia exposure is sequenced with damp heat, thermal cycling, or salt mist testing to simulate multi-contaminant service environments.

FAQ

Which standard governs PV module ammonia corrosion testing?

IEC 62716, "Photovoltaic (PV) modules – Ammonia corrosion testing," is the dedicated international standard for this test. It is applied as a supplementary, environment-specific test alongside the IEC 61215 and IEC 61730 qualification and safety frameworks.

How long does the test take?

The chamber exposure itself lasts approximately four weeks under IEC 62716. Adding initial and final characterization, recovery, and reporting, a complete test campaign typically spans five to seven weeks.

Is ammonia testing mandatory for PV module certification?

It is not part of the baseline IEC 61215 or IEC 61730 test sequences. It becomes necessary when modules are specified for ammonia-rich locations, when a project owner, investor, or insurer requires documented ammonia resistance, or when a manufacturer wants to certify an ammonia-resistant product class.

What kinds of failures does the test reveal?

Typical findings include silver metallization and busbar corrosion, solder joint and ribbon attack, junction box terminal corrosion, encapsulant yellowing from ammonolysis-related chemistry, delamination at material interfaces, elevated wet leakage currents, and accelerated power degradation.

Can ammonia testing be combined with other environmental tests?

Yes. Accredited third-party laboratories frequently offer combined protocols, for example ammonia exposure followed by damp heat or thermal cycling per IEC 61215-2, or salt mist testing based on IEC 60068-2-52 for sites exposed to both agricultural and coastal contaminants.

How many samples are required?

For certification-grade testing, a minimum of two identical full-size production modules is customary, in accordance with the sampling requirements of the applicable standard. Additional samples may be tested in parallel for statistical confidence or combined-stress programs.