COATING ON STEEL STRUCTURES IDEAL AMBIENT CONDITIONS
There are structural steel works that have stayed upward of 100 years and still in perfect condition, the durability of coating on steel structures can only be explained due to some factors that was put into consideration at the outset and preparation of the coating, The surface coating on steel structures is challenging situation from the start, we must give attention to surface preparation.
The environment as key factor in consideration:
First and foremost to have a successful coating on steel structures, the key is in understanding and taking note of the corrosively of the environment to which the structure will be exposed therefore defining the appropriate coating specifications
Coating application, and curing time especially when you work in an unprotected environment. The job of a paint inspector is to find a way to monitor and control the environmental condition of the area. There are several environmental factors to consider during surface coating process. Among the most important are relative humidity, dew point, air and surface temperature. These parameters must be taken into account because they have significant impact on the overall appearance and performance of the project. Furthermore, the continuity, quality, and uniformity of the paint film will be also be determined by the temperature and drying conditions. We are going to look into some of these factors below.
The Temperature of the application environment:
This is the physical quantity expressing the degree of intensity of heat present in the substance or object, especially as expressed according to a comparative scale and shown by a thermeter or perceived by touch. The steel to be coated should maintain at least a temperature of 3*c/5*c to 50*c/60*c above the dew point, but some paint special formulated for cold and hot region can also perform below or above this temperature that is why we should always refer to product data sheet of the material. When you apply a coat of paint to a surface, the paint will absorb heat energy, which then gives the solvents sufficient energy to evaporate from the paint film thereby causing the paint to dry fast. Low temperatures lowers evaporation of liquids from paint. Significant slowing of dry is generally observed with temperatures below but higher temperature can lead to the paint drying fast. Painting in direct sunshine can dramatically increase paint temperature and the speed of dry ,and more faster if the color of the paint is black.High surface temperatures, whether due to exposure to sunlight or service conditions like hot pipes, will also lead to increased speed of dry, and can cause dry spray, mud cracking, and difficulty in maintaining wet edge.
Relative humidity of the application environment
The amount of moisture in the air as compared with the maximum amount that the air could contain at the same temperature, expressed as a percentage. Rh is a measure of water vapor and does not take into account any form of water present such as rain. On a rainy day RH is not 100% as some people may think. High relative humidity that is moisture content of the air retards evaporation of water from paint film. Relative humidity above about 90% can cause extremely slow drying. Excessive humidity can also lead to sagging of the paint, most especially at higher wet film thickness. No final blast or coating should be done if the relative humidity is more than 85% unless stated otherwise in the product data sheet by the manufacturer.
The Dew point
The dew point is the temperature to which air must be cooled to become saturated with water vapor. When further cooled, it will condense to form liquid water. Meterologists use dew points to describe how much moisture is in the air. The temperature that air must cool to in order to reach saturation if the pressure and moisture content are constant. In coating, moisture can form on the surface when the surface temperature is low enough to cause condensation from the atmosphere; the resulting condensation put it at risk of flash rust or oxidation. If the surface already has a fresh coating, the coating might not dry or cure properly. Confirm the minimum and maximum dew point from the data sheet.
Conclusion and final consideration for a satisfactory coatings on steel Structures
Successful coating application requires the monitoring and control of specific ambient conditions like temperature, dew point, relative humidity and strict adherence to the product data sheet of the product as it has to do with ambient conditions and lack of adherence to this environmental and ambient conditions will lead to project delay, poor performance, productivity and budgetary problems.
Epoxy Oilserv Limited is a leading coating company that have successfully completed projects in surface preparation, coating and maintenance of steel structures both in the manufacturing and oil and gas environments, we have completed complex projects in the oil and gas hash environment both onshore and offshore. You may contact us for a free quote at anytime.
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Chemical/Coating development manager
Epoxy Oilserv Limited