DIN 50018 Test in Saturated Atmosphere in the Presence of Sulfur Dioxide (SO2)

The German Standards Institute (DIN) standard, “DIN 50018 Testing in a saturated atmosphere in the presence of sulfur dioxide (SO2)”, describes a method for corrosion testing in a humid, sulfur dioxide (SO2)-containing atmosphere. This method is widely used to evaluate the corrosion resistance of metals, coatings, painted surfaces, metallic materials, and corrosion protection systems under conditions simulating industrial atmospheres, acid rain, or contaminated environments. This method accelerates corrosion processes to quickly reveal weaknesses in protective systems.

This standard is particularly important in industries such as automotive, construction, metalworking, coating/painting, and general manufacturing, where products may be exposed to sulfur-containing contaminants.

The DIN 50018 test method aims to:

• To evaluate the relative corrosion resistance of materials or protective coatings.
• To quickly identify deficiencies in corrosion prevention systems.
• To ensure reproducible results across different laboratories by precisely defining test conditions, equipment, and procedures.
• To simulate the aggressive effects of humid, sulfur dioxide atmospheres (specific to industrial or urban pollution).

Unlike neutral salt spray tests (e.g., DIN EN ISO 9227 standard), this method involves sulfur dioxide, which forms sulfuric acid in the presence of moisture, creating a more aggressive acidic corrosion environment.

This test method subjects the samples to the following cycles:

• Condensation (high humidity, almost 100% relative humidity, usually resulting in water droplets forming on the surface).
• The controlled release of sulfur dioxide gas.
• Drying or ventilation stages (in some variants).

The cycle typically operates as an alternating condensation climate where sulfur dioxide is released during the moist phase. This standard identifies specific variants, indicated by codes such as AHT 1.0 S. Here:

• A = Alternative climate
• H = Heating / condensation phase
• T = Test duration or temperature details
• S = Sulfur dioxide

The number indicates the sulfur dioxide concentration or cycle parameters (e.g., 1,0 litre of sulfur dioxide per test cycle in some common variants). If a specific variant is not specified, AHT 1.0 S is usually the default value.

The basic test conditions (typical parameters) are as follows:

• Temperature during the condensation phase: Usually around 35-40 degrees Celsius.
• Sulfur dioxide dosage: Controlled volume (e.g., 0,2-2,0 liters per cycle depending on the variant).
• Cycle structure: 8 hours of condensation + sulfur dioxide exposure, followed by 16 hours of drying/ventilation (a total 24-hour cycle is common).
• Test duration: Varies from a few cycles to hundreds, depending on the required performance level.
• Chamber volume and sample arrangement are strictly regulated to ensure homogeneous gas distribution and repeatability.

The DIN 50018 standard is closely related to various international standards for sulfur dioxide/moist corrosion testing:

• DIN EN ISO 6988 Metallic and other inorganic coatings - Sulfur dioxide test by general moisture condensation.
• ISO 3231 Paints and varnishes - Determination of resistance to humid environments containing sulfur dioxide.
• ASTM G87 Standard practice for conducting moist sulfur dioxide tests.
• ISO 22479 Corrosion of metals and alloys - Sulfur dioxide test in humid environment.

Applications and typical use cases include:

• Evaluation of zinc coatings, galvanizing, powder coatings, paint systems, and cathodic protection.
• Testing of fasteners, automotive parts, building components, and architectural metals.
• Product qualification for outdoor exposure in industrial or contaminated areas.
• Rapid quality control and comparative ranking of corrosion protection systems.

The test is accelerated and does not perfectly reflect real-world exposure. The results provide comparative performance data rather than absolute performance data. Correlation with field performance depends on the specific environment.

In short, the DIN 50018 standard describes a method for corrosion testing in a condensation environment containing sulfur dioxide. It is widely used to evaluate the corrosion resistance of metallic materials, coatings, and surface treatments under industrial or contaminated atmospheric conditions.

This standard simulates environments in which materials are exposed to the following conditions:

• High humidity
• condensation
• Sulfur dioxide pollutants

These types of conditions are typically seen in:

• Industrial areas
• Urban areas with heavy traffic
• Power plant environments
• Chemical processing plants

The testing method helps determine how well a material or coating resists acidic condensation corrosion.

The DIN 50018 standard describes a cyclic corrosion test performed in a closed chamber. The test environment includes:

• Controlled temperature (typically around 40 degrees)
• High humidity with condensation
• Introducing a specific volume of sulfur dioxide gas into the room.

When sulfur dioxide dissolves in condensed water, it forms sulfurous acid, which aggressively attacks sensitive materials.

The testing process generally follows these steps:

• Sample preparation: Metal panels or finished components must be cleaned and prepared. They must be mounted at a specific angle within the room.
• Gas input: A specific amount of sulfur dioxide (e.g., 0,2 L or 2 L depending on the intensity level).
• Exposure cycle: Typically, 8-hour exposure cycles are applied, followed by rest periods outside the room (usually 16 hours). The total number of cycles depends on the required intensity.
• Evaluation:
• Visual inspection
• Corrosion rating (blistering, rusting, discoloration)
• Possible mass loss measurement

The DIN 50018 standard offers different test intensities. These differ primarily in terms of the volume of sulfur dioxide applied and the number of cycles performed. Higher intensities indicate more aggressive corrosion conditions and faster degradation of unprotected materials.

The DIN 50018 standard is commonly referenced in the following areas:

• Automotive standards
• Manufacturing of household appliances
• Validation of coated steel.
• Testing of galvanized and electroplated parts.
• Paint and powder coating qualification test

In conclusion, the DIN 50018 standard is an important corrosion testing standard used to evaluate material resistance in humid, sulfur dioxide-containing environments. It plays a critical role in quality control and product verification, particularly in industries where atmospheric pollution can significantly affect material durability.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services in accordance with the DIN 50018 standard.