Flexibility is the ability of a coating to resist mechanical damages without cracking, losing adhesion, or failing in some other manner, when it is to be bent, flexed, or stretched in forming operations and/or installation. For pipeline construction, this property is critical because it decides the field-bending limits of the coated pipes and affects the integrity of the installed coatings. In laboratory, flexibility test of pipeline coatings is usually conducted by bending the samples that extracted from coated panels over a pre-determined radius mandrel to produce a short-radius bend. Coating failure is apparent by visual and/or holiday inspection of cracking or loss of adhesion. Two factors that have considerable influence on a coating’s flexibility are temperature and coating thickness.
Test methods for the flexibility are available in:
- CSA Z245.20, Section 12.11
- NACE SP0394, Appendix H
- API RP 5L7, Appendix 13
- API RP 5L9, Appendix I
- ISO 21809-1, Annex I
- ISO 21809-2, Annex A13
- BS EN 10290, Annex K
Test Samples:
1″×8″×0.25″ or 1″×8″×pipe wall thickness (typical)