Different types of coatings are used to protect surfaces from corrosion, wear and tear, and decay. These days, we have a wide range of coatings available for different types of surfaces. Selecting the right coating for a specific application can sometimes be tricky. However, if you want to avoid expensive repairs, it is important to select the right coating.
Before selecting any coating system for your next project, be sure to take a number of factors into consideration. Decisions based on assumptions or lack of information can lead to coating failures, constant maintenance, and unnecessary repairs. Therefore, prior to selecting your coating, important factors such as surface preparation, substrate type, service environment, application process, and desired service life must be taken into account.
Type of substrate: Depending on specific needs of the users, coatings suitable for a wide range of substrates are available. This article is concerned with coatings for mild steel. The tendency for mild steel is constantly to return to its natural state, and the purpose of coatings is both to arrest this decline and the beautify the steel.
Surface preparation: Current state of the substrate also plays a role in selection of the coating. The surface you are looking to protect could be previously coated, rusted, contaminated, or new. Successful application of a new coating depends on your ability to deal with substrate related challenges such as active rusting and failing coating. Class 2.5 abrasive blasting is the benchmark surface treatment, but surface tolerant primers are available where this is not possible.
Application process: The process of application should also be taken into account while selecting the coating. Figure out if you are able to spray. If you are working in a congested space, special safety arrangements may be required for spraying. Also, there can be certain service or environmental factors present during application. Some coatings are formulated specifically for rolling, brushing, and spraying. Some of them are fit for hot applications, and others are not. Therefore, before choosing a coating, carefully review the application process and the limitations for that particular application process.
Service environment: Service environments to consider before coating selection include chemical exposure, temperature, micro environment, insulation, UV resistance, abrasion resistance, immersion requirements, etc. Atmospheric environments are classified into six atmospheric categories based on the corrosion rates of mild steel given in ISO 9223. These are reference in AS2312.1-2014 Guide to the protection of structural steel against atmospheric corrosion by the use of protective coatings. These categories are
Category C1: Very low
Category C2: Low
Category C3: Medium
Category C4: High
Category C5: Very High
Category Cx: Extreme
Service life: Finally, your selection should also be based around how long you want a coating to last. AS2312 expresses durability in terms of the following five ranges, which are an expansion of the three ranges given in ISO 12944-1
Short term: 2 to 5 years
Medium term: 5 to 10 years
Long term: 10 to 15 years
Very long term: 15 to 25 years
Extra long term: 25+ years
If you are still finding it difficult to make the right choice, please contact the experts at A&I Coatings. We are dedicated to providing technologically advanced coating solutions suitable for all types of surfaces and environments.
The following document gives some typical specifications for mild steel.