Adhesive bonding is commonly used across various industries to connect two surfaces safely and effectively. Adhesives are a popular method of bonding two surfaces across industries like oil and chemical, optical, electrical, and electronics due to their ability to form strong and stable bonds to various substrates.

However, one of the crucial factors that can negatively affect the performance of an adhesive is the lack of surface preparation for adhesive bonding. Surface preparation is the process of cleaning and optimising the surfaces where the adhesive will be used. Effective surface preparation removes dirt, dust, oil, moisture, and any other contaminants that can affect the adhesive’s bonding strength. In this blog, we will discuss the role of effective surface preparation for adhesive bonding and some common surface preparation tips.

A] Understanding Adhesive Bonding

Adhesive bonding refers to the process of joining two similar or dissimilar surfaces together with the help of an adhesive. The advancements in adhesive technology have helped to produce high-strength adhesives which can support the weight of large equipment across industries as well as provide reliable adhesion to the smallest electrical components.

Adhesive bonding has numerous advantages over traditional bonding methods; hence, adhesive bonding applications are commonly seen throughout various industries. High-performance structural adhesives like one-component and two-component epoxies and sodium silicate-based adhesives are commonly used adhesives in industrial settings. Selecting the right adhesive and applying it correctly are two of the most essential factors in achieving a good adhesion. And surface preparation is a part of applying the adhesive.

B] The Role Of Surface Preparation

In any industrial setting, before the adhesive is applied to the desired surface, the surface is cleaned and prepared to maximise the adhesive performance. This process is known as surface preparation and is one of the key steps in surface preparation for bonding.

If surface preparation is not conducted effectively, small contaminants like moisture, oil & grease, dirt & dust, and other particles form a wall between the surface and the adhesive applied. Surface preparation also helps to roughen the surface as part of surface preparation. Certain adhesives work better with rough, porous surfaces and might not be able to hold the weight and provide strong adhesion on smooth surfaces. One way that you can increase the adhesive’s performance is to increase the surface’s energy.

C] Common Surface Preparation Methods

Conducting a thorough surface preparation can reduce the chances of adhesive failure and improve the reliability of the equipment. The surface bond can either fail adhesively or cohesively. Adhesive failure occurs when the surface is not adequately prepared and the adhesive detaches itself from the surface. In many industries, adhesive failure can pose safety risks and be more expensive and time-consuming to fix; Hence, it is important to optimize bonding with surface preparation. Here are a few surface preparation methods that you can use to ensure successful adhesive bonding:

1. Cleaning And Degreasing Surfaces

Cleaning and degreasing are essential parts of any surface preparation session. Cleaning and degreasing removes contaminants like dust, dirt, oil, and any other organic matter from the surface of the substrates. Specialized chemicals and cleaning agents are used for thoroughly cleaning the surfaces. Solvents such as methyl ethyl ketone, acetone, and isopropyl alcohol are some of the common cleaning agents used for cleaning and degreasing.

The solvents and techniques used for cleaning can vary depending on the type of substrates, degree of contamination, and type of adhesive to be applied. Physical cleaning methods like plasma treatment are also prevalent. The importance of surface cleaning in adhesive bonding should not be ignored for effective adhesion.

2. Mechanical Methods (Abrasion, Sanding, Grinding)

Mechanical methods of surface preparation include physically altering the surface’s texture to facilitate better adhesion. Mechanical methods such as abrasion, sanding, grinding, etc., help increase the substrate’s surface energy; however, these processes also help remove contaminants and impurities from the surface.

Abrasion, sanding, and grinding help to make the surface more rough and porous, which helps the adhesives maintain their grip on a microscopic level. Mechanical methods also help to remove rust and oxidation from the surface. These processes can be done manually; however, most industries prefer using power tools.

3. Chemical Treatments (Etching, Primer)

Chemical treatments are a popular and effective way of cleaning pollutants from the surface and also creating the desired surface conditions. Chemical treatments such as chemical etching are used throughout various industries to clean metal substrates of loose oxides that cling to the surface and also create a rough surface that can hold the adhesive.

Primers are applied on top of the surface, which helps the adhesive to stick better to the surface. Primers are used to create a desired surface texture on substrates that are difficult to bond.

4. Physical Treatments (Plasma & Flame Treatment)

Physical treatments are used to modify the surface chemistry to improve the substrate’s adhesion. These methods are usually applied on plastic substrates, as chemical and mechanical means can be too harsh for the substrates. For plasma treatment, an ionised plasma gas is released to the surface that reacts with the plastic surface. The plastic substrates react with the particles to create better bonding conditions.

Similarly, flame treatment also helps to alter the surface chemistry and provide better adhesion. For flame treatment, the surface is exposed to fire with the help of a blow torch. Flame treatment increases the surface energy to create better bonding; however, it is a risky method and can harm the substrate.

5. Importance Of Following Manufacturer’s Guidelines For Surface Preparation

Manufacturers’ guidelines are specifically designed to help industries maximise adhesive performance. The adhesive manufacturer knows the best about the adhesive’s properties and performance, and the substrate is best suited for it.

Following the manufacturer’s instructions will ensure safer and more effective adhesive bonding. You can even contact the manufacturer to discuss your specific needs.

D] Factors Affecting Adhesive Bond Performance

1. Surface Energy And Wettability

Surface energy refers to the material’s tendency to adhere to other surfaces. A surface with higher energy will be more effective at sticking to other materials than a material with low surface energy. On the other hand, wettability is the substrate’s ability to spread the liquid adhesive efficiently. It is essential to choose the correct bonding material with high surface energy and wettability. If that is not an option, the surface energy and wettability of a substrate can be increased with effective surface preparation techniques for strong adhesive bonding.

2. Substrate Material Compatibility

Different adhesives exhibit varying degrees of compatibility with different substrates. This means that an adhesive specifically designed for steel or aluminum substrates might not show the same level of adhesion to plastic or ceramic. Conduct thorough research about the adhesives and substrates you are going to use and select the appropriate adhesive for your requirements.

3. Temperature And Humidity Considerations

Temperature and humidity can greatly affect the serviceability of an adhesive. Extreme temperatures affect the viscosity, texture, curing time, and bonding strength of the adhesive. Meanwhile, high humidity can reduce the work time of the adhesive, preventing you from setting the adhesive properly. Moisture and heat can also cause contamination in the adhesive layering, which can cause performance and safety issues.

4. Impact Of Surface Preparation On Bond Strength And Durability

Good adhesive bonding and surface preparation are intertwined with each other. Surface preparation plays an important role in enhancing the substrate’s surface energy and ensuring optimal adhesive performance. Inadequate surface preparation can lead to the formation of weak bonds and adhesive failure. To prevent adhesive failure, enhancing adhesive bonding through surface preparation is crucial. Comprehensive surface preparation includes cleaning the surface of any pollutants and also optimising the surface for adhesives.

Conclusion

The reliability of an adhesive to form strong bonds is a crucial factor for many industries. Surface preparation can help designers and manufacturers across various industries to achieve strong and durable adhesive bonds. There are various methods of surface preparation and selecting the correct methods depending on the substrate and adhesive is crucial.

It is important to consider environmental factors, substrate surface energy, wettability, and substrate durability before surface preparation. Make sure to read and follow the manufacturer’s instructions on surface preparation before applying the adhesive to ensure optimal adhesive bonding.

To find an adhesion solution that is tailored to your unique individual needs, contact us today! Our adhesive experts are always ready to help you find the best solution.

Utsav Shah

Utsav Shah is a 34-year-old entrepreneur with a passion for scientific discovery. Utsav’s journey began with a deep dive into materials science, earning degrees from USC and the Institute of Chemical Technology. He’s the visionary founder of Kohesi Bond, a top-rated adhesive manufacturer, and Cenerge Engineering Solutions, a leader in heat exchangers and cryogenic pumps. With over a decade of experience, Utsav consults across various industries, ensuring they have the perfect adhesive solution for their needs. Connect with him on LinkedIn!