by Types of Pipe Coatings
There are several different types of pipe coatings that are commonly used depending on the application and environmental conditions. Some of the main categories include:
Thermoplastic Coatings
Thermoplastic coatings are tough, flexible polymer coatings that can stretch and return to their original shape without cracking. They are applied as a powder or liquid at ambient temperatures through spray or float methods. Thermoplastic coatings like polyurethane, polyolefin and vinyl ester offer abrasion resistance, chemical resistance and protection against corrosion in many industrial environments.
Fusion Bonded Epoxy Coatings
Fusion bonded epoxy (FBE) coatings are applied as a dry powder and fused to the metal surface using heat. This creates a very durable and protective coating with excellent adhesion. FBE coatings are commonly used for underground pipelines to prevent corrosion from groundwater and soil. They provide barrier protection and are resistant to acids, bases, and salts.
Liquid Epoxy Coatings
Similar to FBE, liquid epoxy coatings are thermosetting polymer coatings that chemically bond to metal surfaces. Pipe Coatings are spray or brush applied as a liquid at room temperature. Once cured, liquid epoxy forms a hard, corrosion resistant shell. Liquid epoxy coatings are often used for above ground pipe applications where FBE is not practical.
Concrete Coatings
Concrete coatings create a hardened shell around pipe surfaces for corrosion protection. Cement mortar coatings involve applying a slurry mixture of cement and sand that air cures to form a concrete-like barrier. Concrete weight coatings use a fluid mixture poured around the pipe to surround it in a heavy concrete shell. These coatings are dense but vulnerable to cracks, making them best for burying in soil or surroundings where impact damage is unlikely.
Three Layer Polyethylene Coatings
Three layer polyethylene (3LPE) coatings consist of an adhesive layer bonded to the metal, a polyethylene powder layer for protection, and an outer weather resistant top layer. 3LPE coatings deliver corrosion resistance and are flexible enough to work with pipe movement. They are well suited foruse in tough offshore oil and gas environments.
Performance Requirements of Coatings
Beyond corrosion protection, pipe coatings must meet certain performance requirements depending on their intended use and environment. Key attributes coatings are specified and tested for include:
Chemical Resistance – The coating must prevent corrosion and withstand exposure to chemicals, acids, alkalis or contaminants it may contact. Test methods evaluate coating properties after chemical immersion/exposure.
Abrasion Resistance – In above ground or abrasive soil conditions, the coating requires hardness and thickness to resist damage from friction or impacts over the lifespan. Taber and fall height tests determine abrasion performance.
Adhesion – Proper surface preparation and coating application ensure adhesion to the substrate. Crosshatch and pull-off adhesion tests quantify bond strength between coating and pipe.
Impact Resistance – Pipelines in handling/transport require coatings resilient enough to withstand impacts without cracking or delamination. Impact and indentation tests evaluate flexibility and toughness.
Dielectric Strength – Insulating or non-conductive coatings are necessary for buried pipes near power lines. Dielectric strength tests measure voltage required to breakdown coating’s insulating properties.
Application and Curing Variables
How coatings are applied and cured significantly impacts their protective capabilities. Variances in these processes can lead to defects, reduced performance or premature failure. Proper control and validation of the following factors is important:
Surface Preparation – Thorough cleaning and abrasion of the pipe surface ensures maximum adhesion of the coating. Degree of cleaning is measured prior to application.
Application Method – Properties like thickness and coverage depend on the spray equipment, line speeds and application variables being correctly calibrated.
Curing Conditions – Heat treating, exposure times and temperatures during curing must achieve full polymerization and crosslinking of coating constituents as specified.
Holiday Detection – Post-application testing uses high voltage to detect any pinholes, cracks or thin spots in coatings, especially on welds and seams.
Coating Thickness – Too thin provides insufficient protection, too thick wastes material and creates operational issues. Coating thickness is closely controlled and measured.
Quality Assurance and Testing
Considering the critical role of external coatings, quality assurance practices and various tests are conducted throughout the coating process:
– Surface Preparation Quality – Blast profile measurement on mill certified test panels validate cleaning method.
– Application Control Tests – Density checks ensure proper coatings viscosity and spray parameters like thickness and coverage.
– Cure Verification – Samples undergo FTIR, DSC or TG analysis to prove curing chemistry completed as formulated.
– Adhesion Tests – Crosshatch or pull-off tests quantify bond strength of field coated samples post-cure.
– Holiday Detection – High voltage spark tested to locate holidays before backfilling in field installation.
– Accelerated Weathering – Coated witness panels submerged or exposed to sun/weather to verify integrity over time.
– Operation & Maintenance Requirements – Proper coating storage, handling and repair practices specified to maintain protection.
Proper quality assurance confirms external coatings perform their critical role of corrosion prevention and protection of pipeline infrastructure assets for decades of reliable service life. Adhering to coating standards and test specifications ensures pipelines remain intact wherever buried or transported over variable field conditions.
Article has provided an overview of common pipe coating types used in industry, highlighted important performance requirements, and discussed factors important for application, curing and quality assurance of external corrosion protective coatings on pipe surfaces. Selecting the right coating system and validating its quality through testing protects pipelines from corrosion failures and allows them to safely transport critical fluids throughout their design lifespan.
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
About Author - Alice Mutum
Alice Mutum is a seasoned senior content editor at Coherent Market Insights, leveraging extensive expertise gained from her previous role as a content writer. With seven years in content development, Alice masterfully employs SEO best practices and cutting-edge digital marketing strategies to craft high-ranking, impactful content. As an editor, she meticulously ensures flawless grammar and punctuation, precise data accuracy, and perfect alignment with audience needs in every research report. Alice's dedication to excellence and her strategic approach to content make her an invaluable asset in the world of market insights. LinkedIn
