ReviewEvaluation of the cathodic disbondment resistance of pipeline coatings – A review
Introduction
Pipelines are an integral component of our modern society as they provide the most practical and the safest way of delivering oil and gas [1] to satisfy the energy demands of our daily life. Take Canada for example: approximately 1.2 billion barrels (∼ 190 billion liters) of liquid petroleum products and 5.3 trillion cubic feet (∼ 150 trillion liters) of natural gas are transported by pipelines each year [2]. In 2015, the total economic impact from the operation of all of the energy transmission pipelines in Canada on GDP was estimated to be about $11.5 billion (about 0.7 % of the total GDP) [3]. The long-term integrity of pipelines is therefore of significant economic importance. As steel pipes tend to corrode when exposed to moist soil or wet air, applying coatings on the surface of pipes is the primary approach to defend them against corrosion. Coatings provide a physical and electrochemical barrier between the steel surface of the pipe and the surrounding environment. However, defects in pipeline coatings are unavoidable at every stage of the coating process, the pipe installation and operation of the pipeline. A discontinuity in pipeline coatings is referred to as a “holiday”. Once a holiday exposes bare metal to the surrounding environment, corrosion can occur. This is where cathodic protection (CP) becomes important. CP enforces a cathodic current at the coating defect sites to protect the steel pipe from corrosion so that it cannot become an anode. Therefore, for immersed and buried pipelines in the field, a combination of protective coatings and CP is almost always adopted to defend against corrosion. Nevertheless, depending on the nature of the defect and the surrounding environment’s chemistry, cathodic current provided by CP may result in reaction products that can affect adhesion of the coating around the defect and cause so called cathodic disbondment (CD), which is considered to be the most significant degradation mechanism for organic coatings on submerged steel [4]. Since the performance of a coating system directly affects the integrity of the pipelines it protects, it is essential to evaluate coating performance in conditions encountered during the installation and operational life of pipelines. As a consequence, ex-situ CD tests as well as in-situ CD assessment have been developed through the years to assess coating performance before and after service in the field. Ex-situ CD tests provide a basis with which to judge the resistance of coatings to CD and thus act as a practical tool to select pipeline coatings. In-situ CD assessment offers a way to monitor a coating’s performance non-destructively and is useful in aiding the maintenance of pipelines in the field, such as via the adjustment of applied CP potentials.
In this review, fundamental aspects of CD are first introduced, focusing on a discussion of the proposed mechanisms. Following this, ex-situ CD test methods including both the standard and modified methods are examined. The influence and the significance of test parameters on the disbondment rate is analyzed to reveal the advancement of the standard test methods. The need for developing modified CD test methods as well as their contribution to coating evaluation is discussed. The potential use of these ex-situ CD test methods to compare the disbondment resistance of coatings, e.g., fusion bonded epoxy (FBE) and high-performance powder coating (HPPC) is also presented. The third part of this review introduces various in-situ techniques to monitor the CD behavior of coatings, compares the pros and cons of each technique and addresses the development of two techniques in particular, i.e., electrochemical impedance spectroscopy (EIS) and electrochemical measurement using a wire beam electrode (WBE). As the mitigation of CD as well as ensuring pipeline integrity are the ultimate goals of any research in this field, the final section discusses strategies that have been used to achieve these goals in terms of coating selection and cathodic protection adjustment. This discussion further highlights the importance and necessity of using the proper CD test for a given situation.
Section snippets
The mechanisms of CD
CD occurs on coated metals that are cathodically protected. CD refers to the failure of adhesion at the coating/substrate interface, which is directly related to the application of CP [5,6]. The mechanistic study of CD reveals how the disbondment commences, shedding light on the methods that may mitigate it.
CD is often initiated by the formation of defects due to accidental coating damage during pipeline handling and installation or imperfect application, leading to excessive permeability of a
Ex-situ evaluation of CD resistance of coatings
Once the coatings have cathodically disbonded, corrosive gases, water, and reactive species may enter the disbonded area and cause pipeline corrosion [[31], [32], [33], [34]]. It is therefore essential to evaluate the CD resistance of coatings when selecting them for use on pipelines. CD tests are designed with relevant test parameters to investigate their effects on the rate of coating disbondment and to provide a reliable assessment of the coating quality. This section discusses both standard
In-situ assessment of CD of coatings
CD test methods provide an efficient way of predicting coating performance and therefore offer useful guidance for coating selection. On the other hand, it is important to note that the present CD test methods are all destructive ex-situ laboratory based tests, which have limitations in accurately predicting the disbondment behavior of coatings in service. For field monitoring of coating disbondment, the use of in-situ techniques (non-destructive methods) is preferred, as these are able to
Mitigation of CD and corrosion under the disbonded coating
For cathodically protected pipelines with coatings, an appropriate amount of CP is able to reduce corrosion to less than 0.01 mm per year [92] and a good quality coating can decrease the current required for protection by a factor of 1000 or greater [93]. However, excessive CP can lead to coating CD, and insufficient CP cannot provide effective corrosion protection [94]. Therefore, the coating resistance to disbondment, the applied CP level, as well as the compatibility of coating and CP after
Summary
Protective coatings and CP are used simultaneously on pipelines to prevent them from corrosion. However, CD, i.e., the loss of adhesion of coatings on the metal substrate, appears as an adverse side effect of the combination of coatings and CP. The application of ex-situ CD tests as well as in-situ techniques to assess the performance of pipeline coatings plays a vital role in mitigating CD and helps to guarantee and maintain the pipeline integrity. Fig. 24 illustrates the effects of coating
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
The authors acknowledge funding support from the Natural Sciences and Engineering Research Council (NSERC) of Canada [NSERC CRDPJ 503725-16]. The funding and in-kind support from Shawcor Ltd. and Specialty Polymer Coatings Inc. [Industry portion - NSERC CRDPJ 503725-16] is also greatly appreciated.
References (114)
- et al.
The mechanism for the cathodic delamination of organic coatings from a metal surface
Prog. Org. Coat.
(1983) - et al.
Cathodic disbondment resistance with reactive ethylene terpolymer blends
Prog. Org. Coat.
(2007) - et al.
The effect of surface modification on the cathodic disbondment rate of epoxy and alkyd coatings
Prog. Org. Coat.
(2005) - et al.
The application of x-ray photo-electron spectroscopy to a study of interfacial composition in corrosion-induced paint de-adhesion
Corros. Sci.
(1981) Paint adhesion, corrosion protection, and interfacial chemistry
Prog. Org. Coat.
(1994)- et al.
Understanding the effects of applied cathodic protection potential and environmental conditions on the rate of cathodic disbondment of coatings by means of local electrochemical measurements on a multi-electrode array
Prog. Org. Coat.
(2017) - et al.
Influence of substrate topography on cathodic delamination of anticorrosive coatings
Prog. Org. Coat.
(2009) - et al.
Cathodic delamination: quantification of ionic transport rates along coating–steel interfaces
Prog. Org. Coat.
(2010) The application of impedance methods to study the effects of water uptake and chloride ion concentration on the degradation of paint films—I
Attached films, Corrosion Science.
(1991)- et al.
The delamination of polymeric coatings from electrogalvanized steel – a mechanistic approach. Part 2: delamination from a defect down to steel
Corros. Sci.
(2001)
Chemical and electrochemical conditions on steel under disbonded coatings: the effect of previously corroded surfaces and wet and dry cycles
Corros. Sci.
A study on cathodic protection against crevice corrosion in dilute NaCl solutions
Corros. Sci.
Physicochemical parameters influencing the testing of cathodic delamination resistance of high build pigmented epoxy coating
Prog. Org. Coat.
Characterization of high performance composite coating for the northern pipeline application
Prog. Org. Coat.
Localized electrochemical characterization of organic coatings: a brief review
Prog. Org. Coat.
Breakdown of organic coatings in corrosive environments examined by scanning kelvin probe and scanning acoustic microscopy
Electrochim. Acta
Degradation of organic coatings in a corrosive environment: a study by scanning Kelvin probe and scanning acoustic microscope
Prog. Org. Coat.
A cathodic delamination study of coatings with and without mechanical defects
Corros. Sci.
An impedance spectroscopy study of the degradation mechanism for a model epoxy coating on mild steel
Prog. Org. Coat.
Electrochemical impedance spectroscopy as a tool to measure cathodic disbondment on coated steel surfaces: capabilities and limitations
Prog. Org. Coat.
Assessment of organic coating degradation via local impedance imaging
Electrochim. Acta
A new technique able to measure directly the delamination of organic polymer films
Corros. Sci.
Characterization of corrosion of X65 pipeline steel under disbonded coating by scanning Kelvin probe
Corros. Sci.
Mechanism of cathodic delamination control of zinc–aluminum phosphate pigment in waterborne coatings
Corros. Sci.
Modified wire beam electrode: a useful tool to evaluate compatibility between organic coatings and cathodic protection
Prog. Org. Coat.
The effects of addition of poly(vinyl) alcohol (PVA) as a green corrosion inhibitor to the phosphate conversion coating on the anticorrosion and adhesion properties of the epoxy coating on the steel substrate
Appl. Surf. Sci.
The role of post-treatment of an ecofriendly cerium nanostructure Conversion coating by green corrosion inhibitor on the adhesion and corrosion protection properties of the epoxy coating
Prog. Org. Coat.
Inhibition of corrosion driven delamination on iron by smart-release bentonite cation-exchange pigments studied using a scanning Kelvin probe technique
Prog. Org. Coat.
Effect of zinc-free phosphate-based anticorrosion pigment on the cathodic disbondment of epoxy-polyamide coating
Prog. Org. Coat.
The impact of pigment volume concentration on the protective performance of polyurethane coating with second generation of phosphate based anticorrosion pigment
Prog. Org. Coat.
Pipelines are safest for transportation of oil and gas
Manhattan Inst. Policy Res. No.
Committed to Safety-committed to Canadians, 2015 Pipeline Industry Performance Report
Angevine Economic Consulting Ltd., Economic Impacts From Operation of Canada’s Energy Transmission Pipelines
Corrosion Control Through Organic Coatings
Practical Analysis of Cathodic Disbondment Test Methods
Comparison of Cathodic Disbondment Test Methods for Water Infrastructure Coatings
Corrosion Prevention by Protective Coatings
Distribution of steady-state cathodic currents underneath a disbonded coating
Corrosion.
The application of X-ray photoelectron spectroscopy to the study of polymer-to-metal adhesion. Part 2. The cathodic disbondment of epoxy coated mild steel
J. Mater. Sci.
Interfacial chemistry of the corrosion of polybutadiene-coated steel
Ind. Eng. Chem. Prod. Res. Dev.
Reduction of cathodic delamination rates of anticorrosive coatings using free radical scavengers
J. Coat. Technol. Res.
Technical note: the mechanism of cathodic disbondment of protective organic coatings—aqueous displacement at elevated pH
Corrosion.
Mechanism of cathodic disbonding of three-layer polyethylene-coated steel pipe
Corrosion.
Interface chemistry of stoved organic coatings
Ind. Eng. Chem. Prod. Res. Dev.
Mechanism of Disbonding of Pipeline Coatings
Towards a better understanding of corrosion beneath organic coatings
Corrosion.
Effect of zeta potential on adhesion of organic coatings
Corrosion.
Evaluation of global cathodic protection criteria-part 1
Criteria and Relevance With Cathodic Protection Theory
Analysis of CDT Methods and Factors Affecting Cathodic Disbondment
Role of hydrogen and hydroxyl ion in cathodic disbondment
Anti-corrosion Methods Mater.
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