Hello Pipe Enthusiasts!
This article covers eleven coating tests commonly used in the steel pipe industry, especially for oil, gas, and underground construction applications. Here are some key terms in Quality Control of Coated Steel Pipe at PT. Bakrie Pipe Industries:
1. Tensile Test
Tensile Test is used to measure the tensile strength of the protective coating on steel pipe. This test determines how much stress the material can withstand before permanent deformation or failure occurs. The results provide an indication of the coating’s resistance to external forces during transportation and installation.
In the context of coated steel pipe, the tensile test also helps assess the quality of adhesion between the coating and the steel substrate. Coatings with low tensile strength risk delamination or cracking under mechanical pressure, making this test an important indicator in the inspection process.
2. Heat Aging Test
The Heat Aging Test simulates the thermal aging conditions a coating experiences over its service life. Samples are subjected to elevated temperatures for a specified duration to observe changes in physical and chemical properties such as hardness, elasticity, and color. The objective is to ensure the coating remains stable and does not degrade under high-temperature exposure.
This test is especially relevant for pipes installed in tropical climates or extreme heat environments. Coatings that fail heat aging may develop microcracks or lose flexibility, accelerating corrosion on the underlying steel.
3. Flow Rate Test
Flow Rate Test measures how quickly fluid or gas passes through a coated pipe system. Although not a direct coating integrity test, its results can reveal surface irregularities caused by uneven or overly thick coatings.
In industrial applications, maintaining optimal flow is critical for operational efficiency. Coatings that impede flow can raise internal pressure and energy consumption, so this test ensures the protective layer does not compromise hydraulic performance.
4. Moisture Content Test
The Moisture Content Test determines the amount of water absorbed by the coating layer. High moisture levels can trigger chemical reactions that weaken the coating structure, such as hydrolysis or blister formation. This test is performed using gravimetric methods or moisture sensors.
Coatings with excessive moisture uptake are prone to delamination and loss of insulating properties. Therefore, moisture testing is an essential step in pre-shipment inspections, especially for underground or subsea pipeline applications.
5. Cathodic Disbondment Test
Cathodic Disbondment Test evaluates how well a coating resists detachment from the steel surface when exposed to cathodic protection current. This test replicates field conditions where electrical systems are used to prevent corrosion. Coatings that cannot withstand the applied current will disbond, leaving steel exposed.
The outcome provides insight into the coating’s electrochemical stability. Coatings that pass this test demonstrate strong adhesion and long-term durability, making them ideal for buried pipelines and other cathodically protected systems.
6. Flexibility Test
Flexibility Test assesses a coating’s ability to withstand deformation without cracking or peeling. Steel pipes often undergo bending during installation, so the coating must be flexible enough to conform without losing its protective properties.
This test is typically carried out using bending or mandrel methods. Coatings that are too rigid crack easily, while overly soft coatings may lack mechanical strength. Achieving the right balance between flexibility and toughness is key to optimal coating design.
7. DSC Test (Differential Scanning Calorimetry)
DSC Test analyzes the thermal properties of a coating, including melting point, glass transition temperature, and thermal stability. By heating the coating sample in a controlled manner, the DSC instrument records energy changes that reveal material characteristics.
This test ensures the coating does not undergo phase transitions or degradation when exposed to high temperatures. Data from DSC helps select coating materials suited to the pipe’s operational environment.
8. Impact Test
Impact Test measures a coating’s resistance to sudden mechanical impacts. During handling and installation, pipes can collide with hard objects or rough surfaces. A coating that withstands impact will better protect the steel from mechanical damage and subsequent corrosion.
This test involves dropping a defined weight onto the coated surface and inspecting for cracks, delamination, or deformation. Coatings that pass demonstrate high performance under dynamic, unpredictable field conditions.
9. Adhesion Test
Adhesion Test evaluates the strength of the bond between the coating and the steel substrate. Common methods include pull-off, cross-cut, or tape tests. Good adhesion prevents the coating from peeling off under stress, moisture, or temperature fluctuations.
In steel pipe inspection, adhesion is a primary indicator of coating quality. Poorly adhered coatings can delaminate, accelerating corrosion and drastically reducing the pipe’s service life.
10. Indentation Test
Indentation Test measures a coating’s resistance to localized pressure or point loads. In this test, an indenter is pressed into the coated surface with a specified force, and the resulting impression’s depth or diameter is analyzed. The goal is to determine how well the coating withstands mechanical stress without structural damage.
This test is crucial for ensuring that the coating does not easily scratch or deform when the pipe contacts hard objects or experiences pressure during storage and transport. Coatings with high indentation resistance better protect the steel from abrasion and local deformation that can initiate corrosion.
11. Holiday Test
Holiday Test is a non-destructive method for detecting microscopic defects or pinholes in the coating that are not visible to the naked eye. A low-voltage electrical current is applied to the coated surface; if there is a gap or uncoated area, current flows to the steel substrate and triggers a detection signal.
Holiday testing is essential to verify that the coating fully covers the pipe surface without any voids that could act as corrosion initiation sites. This method is commonly used on Fusion Bonded Epoxy (FBE), Three Layer Polyethylene (3LPE), and Three Layer Polypropylene (3LPP) coated pipes before shipment, serving as the final quality-validation step.
Coated Steel Pipe Testing at BPI
Through a series of comprehensive coating tests, from Tensile Test through Holiday Test, Bakrie Pipe Industries ensures each coated steel pipe produced offers optimal resistance to mechanical stress, extreme environments, and long-term corrosion potential. These tests not only meet technical standards but also guarantee product reliability in the field.
With complete, state-of-the-art laboratory facilities and ISO/IEC 17025:2017 certification, BPI remains committed to providing the best inspection and testing solutions for Indonesia’s steel pipe industry. If you need technical support or coating testing services for your project, our expert laboratory team is ready to assist you.
That concludes the important terms in the steel pipe inspection process (Part 4), specifically related to quality control of coated steel pipe such as Fusion Bonded Epoxy (FBE), Three Layer Polyethylene (3LPE), and Three Layer Polypropylene (3LPP).
That’s it for today’s session, see you in the next edition! Don’t hesitate to share your insights in the comments, and keep following the latest updates on steel pipe technology exclusively at #BPIPipeInsights.
