Coating curing: the 5 fundamental aspects
Verniciatura a polvere: cos’è e come funziona

Coating curing: the 5 fundamental aspects

Coating curing: the 5 fundamental aspects

3 November 2021

In this article we are going to examine the last step of the industrial coating process, which is often taken for granted and which deserves to be examined in depth: the polymerisation phase in the curing oven, in which the paint is permanently deposited on the substrate.

In order for an industrial coating process to become an added value, attention must be paid to all stages of the process. This applies as much to powder and liquid coating as to e-coating. From the initial selection of the best raw materials to the maintenance of the infrastructure, everything must be perfectly assessed so that nothing compromises the quality of the coating.

 

In this article we are going to examine the last step of the treatment, which is often taken for granted and which deserves to be examined in depth: the polymerisation phase in the curing oven, in which the paint is permanently deposited on the substrate.

 

Curing is a fundamental process to maximise the performance of coatings, achieving adhesion, chemical resistance and the necessary surface properties, all of which can only be achieved if the process is carried out correctly, according to the technical indications of the various types of paint applied.

 

There are at least five factors that should be carefully monitored to help achieve proper cure. Let’s look at them together.

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1. Substrate temperature

Having to go inside an oven, the first factor that is easy to think about is the temperature of the oven itself; instead, probably the most important aspect of curing is the temperature of the substrate, as it is the substrate that heats up causing the coating to harden. The time required to reach the correct substrate temperature varies according to the type of material and its weight.

 

2. Oven temperature

The oven temperature during curing is also critical. It is important to know that the temperature of an oven can often vary depending on the air flow and the size of the batch to be polymerized as well as, inevitably, on the type of material being treated and the coating method chosen: for example if you is following a cycle of liquid painting, powder coating or cataphoresis.

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3. Curing time

This aspect must also be carefully checked, as there tends to be an inverse relationship between polymerization time and temperature. For example, some materials, such as castings, can cause bubbles when subjected to high curing temperatures and therefore require lower temperatures for longer periods. On the other hand, the lowering of the polymerization temperature could change the characteristics of the coating film, and a prolonged polymerization could degrade the coatings. These effects are some examples to better understand how the polymerization time is essential and calibrating it at best is invaluable for the correct deposition of the coating.

 

4. Airflow

There are at least two reasons why you need to pay attention to the air flows in the curing oven. On the one hand, it helps to maintain the same temperature throughout the oven, thus eliminating any “dead” areas that can prevent proper polymerization; on the other hand, the airflow must be controlled so that the fumes are emitted through the exhaust systems and do not escape into the work environment where they could cause a health hazard.

 

5. Loading the oven

The load of the oven is also a factor to be evaluated: as the volume of the items to be treated increases, polymerization will take longer. To give an example of how this can affect, a heavy load in a line oven may require a slowdown in the speed of the production line.

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As we have seen, achieving ideal curing is not always easy due to the many variables involved. For this reason, relying on an experienced and trusted partner is essential.

 

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