How to implement glue into production? Adhesive standard DIN 2304

How to implement adhesive bonding in production? DIN 2304 bonding standard

DIN 2304 was introduced in March 2016. It is linked to the ISO 9001 quality management system and applies to all industrial sectors where bonded joints are used. It can be compared to DIN 6701, developed for the railway sector. Its purpose is to establish standards that enable the preparation and implementation of repeatable and reliable bonding processes. The standard also supports process identification, error analysis, strengthens quality awareness among employees, and structures the approach to testing and validation.

Key takeaways

✅ DIN 2304 organizes bonding responsibilities and process management in production (aligned with ISO 9001)

✅ Bonding is considered a “special process” — without destructive tests and ageing tests, durability cannot be fully verified

✅ The standard introduces safety classes S1–S4 based on the consequences of joint failure

✅ Responsibility for the bonding process lies with the user (the plant), not the adhesive supplier

 

DIN 2304 describes the state of the art in organizing bonding-related processes within a production facility. In the meaning of this standard, bonded joints are material joints made using adhesives whose primary function is to transfer mechanical loads. This function should ensure the product’s performance and safety throughout its entire life cycle.

According to the standard, bonding is a special process. This means that the quality and durability of a bonded joint cannot be fully assessed using non-destructive methods alone. In practice, without destructive (pull/tear) tests and ageing tests, it is not possible to clearly determine the long-term durability and strength of the adhesive bond and the entire joint.

Many variables influence the bonding process and the final joint performance. Each factor may significantly affect the outcome, and thus the success of the production process. An additional challenge is that many industrial adhesives are polymers that age over time, for example under the influence of moisture. This ageing can weaken both adhesion and cohesion. In practice, this means that selection should consider not only the adhesive itself, but also the substrate, operating conditions, and application method.

For more demanding substrates, a helpful reference is our guide on bonding plastics. Additional context can also be found in the article about bonding stainless steel instead of welding.

It is commonly assumed that up to 90% of bonding process failures result from application errors rather than defects of the adhesive product itself.

 

Bonding is often compared to welding technology. In welding, there is a structured and hierarchical personnel qualification system, formalized and certified by international standards. People involved in welding are properly trained and aware of their responsibilities.

For bonding processes, a similar responsibility and qualification concept exists—ranging from execution level, through supervision and management, up to technical decision-making. These qualification levels are internationally recognized, consistent with ISO 17024, and independent of industry and product type. In Europe, harmonized qualifications include: European Adhesive Bonder (EAB), European Adhesive Specialist (EAS), and European Adhesive Engineer (EAE).

ISO 17024 describes personnel certification principles and is an important reference point for organizations that implement bonding technology correctly in production.

 

Safety requirements for bonded joints

The safety classification of bonded joints is performed by the designer or the person responsible for the component. The assessment considers the potential consequences of bonded joint failure.

S1 – high safety requirements

Joint failure leads directly or indirectly to an unavoidable threat to health or life. It may also lead to loss of function with a high likelihood of such a threat.

S2 – medium safety requirements

Joint failure may lead to a direct threat to health or life. Loss of function may involve harm to people or serious environmental damage.

S3 – low safety requirements

Joint failure causes loss of function whose consequences are unlikely to involve harm to people or serious environmental damage. At most, it may result in loss of comfort, performance, or minor property damage.

S4 – no safety requirements

Joint failure causes loss of function whose consequences, under foreseeable conditions, are not associated with harm to people or the environment. The result may only be loss of comfort or performance without significant property damage.

According to Professor Andreas Groß from Fraunhofer IFAM, DIN 2304 can also be helpful in legal disputes regarding compensation. It specifies ISO 9001 quality requirements and defines principles for proper bonding process management. Implementing the standard reduces the number of errors and can lower costs. Companies working according to DIN 2304 also build greater prestige and trust among partners and end users.

 

Who is responsible for compliance with DIN 2304?

Responsibility for the bonding process lies solely with the user of the product. This responsibility cannot be transferred to the adhesive supplier. The adhesive manufacturer’s role is to provide a product that meets the specification described in the technical data sheets, delivered under appropriate conditions with documented product quality.

After delivery to the customer, the manufacturer is not responsible for how the product is used, because they have no control over application conditions or the actual use case. The supplier may advise on possible solutions, but should not make technological decisions for the user or take responsibility for them. They also should not be involved in legal constructions intended to bypass the responsibility assigned to the user in DIN 2304.

 

FAQ – DIN 2304 in practice

How is DIN 2304 different from “standard” quality requirements?

DIN 2304 structures bonding process organization, responsibilities, and risk/safety approach for bonded joints, complementing ISO 9001 with practical process expectations.

Why is bonding called a “special process”?

Because the quality and long-term durability of the joint cannot be fully verified using non-destructive methods alone. In practice, destructive tests and ageing tests are needed to validate durability.

What do S1–S4 safety classes mean?

They classify bonded joints by the consequences of failure: from very high safety requirements (S1) to no relevant safety requirements (S4).

Who is responsible for bonding in a production plant?

According to the standard’s concept, responsibility lies with the user (the plant). The supplier is responsible for product quality/specification, but not for application conditions and process execution.