The role of desiccant dehumidification in industrial coating and surface protection

by Atul Bansal, Chief Operating Officer, Technical Drying Services

Corrosion can be defined as the degradation of a metal due to a reaction with its environment. Metal corrosion accelerates significantly in humid environments due to interactions between moisture, oxygen, and metal surfaces.

A common oxidation reaction in corrosion is the oxidation of neutral iron atoms to positively charged iron ions. The electrons lost from a metal must go somewhere, and they usually end up on a non-metallic atom forming a negatively charged non-metallic ion. Because the charge of these ions has become smaller (more negative charges) the ion or atom which has gained the electron(s) is said to have been reduced.

While other reduction reactions are possible, the reduction of oxygen is involved in well over 90% of all corrosion reactions. Thus, the amount of oxygen present in an environment, and its ability to absorb electrons, is an important factor in determining the amount of oxidation, or corrosion, of metal that occurs.

Here, moisture is a major threat that comes with the ability to deteriorate the coating layer, necessitating humidity control within the setup ranging from tanks to columns, reactors, vessels, pipelines, etc. Delving deep into it, humidity is responsible for causing inadequate surface preparation that gives rise to the issue of blistering, cracking, peeling, and cratering on the surface hence, shrinking the lifespan of the coating system, moisture resists adhesion between the substrate and the coating, which is indicative of the fact that improper surface preparation is a major contributor to major premature coating failure.

Understanding that tanks in a factory setup store expensive, sensitive and reactive chemicals such as petrochemicals and chemical gases, etc, improper coating wears off the surface and results in the dilution and contamination of products. The complications get further exacerbated during monsoon and night, when there is a spike in humidity on account of cold & humid weather. This consequently triggers condensation on metal surfaces, ultimately giving rise to corrosion, commonly known as rust bloom or flash rust. Moreover, carrying out painting on condensed surfaces culminates in blistering and delamination problems.

Therefore, steps for humidity and temperature control involves blasting for exercising corrosion control and holding the blast. During painting & coating, it helps in better quality and adhesion at substrate and at the time of curing, it ensures faster curing.

Considering that coating and painting success majorly hinges on efficient surface preparation, it becomes a prerequisite to eliminate humidity at the time of preparation. Installing desiccant dehumidifiers can come in handy for ensuring the removal of moisture by controlling relative humidity (RH) and dew point throughout the process. In order to drive optimal industrial coating, the technology achieves stringent environmental conditions, meeting the technical specifications of the industry aimed at bringing the desired coating and painting outcomes.

The desiccant dehumidification technology limits the RH below recommended 55% for controlling coating defects. At the same time, it attains a dew point differential of -5° C between the air and surface temperature of the surface to be coated. Along similar lines, it also achieves a -12° C dew point differential between air inside the tank or pipelines and outside air.

All in all, desiccant dehumidification systems oversee proper surface preparation, enabling effective coating application, leading to an efficient painting process. It plays a crucial role in alleviating condensation and rust bloom issues at the time of conducting the painting process, this benefit of curbing blistering and curing failures facilitates strong intercoat adhesion , thereby improving coating life.