In late 2014, the American Petroleum Institute revised API 652 to address practices recommended for maintenance relining of aboveground storage tanks (ASTs) with the objective of achieving a minimum 20-year lifecycle coating performance.
Adherence to fundamentals and conformance to work specifications of tank relining projects will generate significant cost savings during the lifetime of the tank, which is important to lowering the total cost of ownership. Properly applied protective coatings mitigate the potential for corrosion and the consequential impact of environmentally damaging leaks, as well as the contamination of the product in storage.
A documented, fundamental and leading cause of coating failures is the presence of residual, nonvisible, soluble surface salts not identified or removed during the critical surface preparation step immediately prior to the protective lining application. Tanks in service have and will accumulate various soluble salts. The impact of their potential presence requires the incorporation of ion-specific testing in the work specifications as an important determinant of how to proceed in completing the surface preparation and cleaning step of the tank relining project.
Every maintenance coating project, either for atmospheric service or in more severe immersion service, should be reviewed and revised as necessary to clearly include surface testing for residual surface salts and their removal prior to coating application. A well-defined and accurate test method should be called out that can measure specific anionic species in single µg/cm2 digits and at locations where pitting or corrosion is prevalent or can be expected. Levels above this will require a decontamination step that can be easily accomplished with an environmentally safe and easy-to-use acidic soluble salt remover. Testing, also recommended after decontamination to ensure the operator has applied the product as stated in written guidelines, should be done by a qualified third-party inspector or trained staff member to ensure the interests of the owner are best served.
Early adopters, who have incorporated testing and remediation of salts and other practices outlined in the revisions to API 652, have benefited significantly from the cost savings associated with the elimination of premature coating failures. As an example, for very large tank relining projects that can easily exceed $1 million, prior relining cycles of every five to seven years have been eliminated. Linings installed under the revised regimen of testing and decontamination are in their 20th year and are expected to achieve a 25-year minimum lifespan. The financial impact of these maintenance cost savings, as well as the deferral of asset utilization loss and administrative and overhead savings, cannot be overlooked.
It is noteworthy this subject has received much attention and those intimately involved — inclusive of coating manufacturers that design and develop protective coatings for various conditions and circumstances — agree about the importance of surface cleanliness for the proper performance of coatings. It is unfortunate, though, that somewhere in the communications between all the parties concerned during the early phases of a project design and execution, the owners’ interests and objectives may not be fully taken into account. As a result, the owner is left with the financial burden of a premature coating failure, regardless of assurances or other tacit legal protection. In summary, owners have a fiduciary duty to ensure the lowest cost of ownership of long-term assets, and that includes the incorporation and execution of proven best management practices.
For more information, contact Hap Peters at hpeters@chlor-rid.com, or visit www.chlor-rid.com.
