Corrosion Basics: Coating Condition Surveys

In view of the costs involved, maintenance personnel must establish and follow engineered and consistently applied processes in evaluating structures and the corrosion protection system used on them.

The application of new coating systems or the maintenance of existing protective coating systems on structures or facilities should not be started without a thorough understanding of exactly what conditions exist and how these conditions could affect the ability of the coating systems to adequately protect the structure. Additional investigation into the causes of any premature failure or lack of performance of the installed coatings should also be considered.

Degradation of structures and facilities caused by corrosion represents a significant challenge to maintenance personnel. Maintenance actions must address getting the maximum benefit from the installed protective coating systems and ensure that the degradation of the substrate does not lead to inherent safety hazards or interruption of operations.

The first step of a maintenance program is typically a condition survey. Unfortunately, too often this survey consists of a simple walk through or around the facility to get a visual picture of what the structure looks like from just an aesthetic viewpoint. It is quite often done from the viewpoint of how the neighborhood views the facility, rather than from how well the structure is resisting the effects of corrosion with an emphasis on its preservation. The reasons for conducting the survey may include:

• Preparation for overhaul or other scheduled activity

• Periodic assessment to monitor system performance

• Report of a failure to the coating system or structural element

A proper survey requires dividing the structure or facility into easily defined components or groups of components (e.g., a logistical grouping of manageable parts that will be painted together), then proceeding in a methodical fashion to establish exactly what has happened to the structure and the coating systems, and why, since its last painting program.

In view of the costs involved, maintenance personnel must establish and follow engineered and consistently applied processes in evaluating structures and the corrosion protection system used on them. These processes establish guidelines for the surveyor gathering data in the field.

Planning and engineering personnel will use the data collected to select, prioritize, budget, program, and execute maintenance projects in the most cost-effective manner. More in-depth inspection may be required to properly evaluate the significance of degradation observed based on the initial survey. Accurate root cause analysis can be critical in developing effective remedial action that will avoid, or delay, a recurrence of the discovered damage.

Planning for the Condition Survey

Several elements of preplanning will be necessary to effectively execute the condition survey. The first is a logical breakdown of the facility and the second is to have a grading system to evaluate the observed conditions.

Facilities and structures vary in complexity. The breakdown of each facility or structure, in terms of establishing the corrosion protection system grade, will vary by complexity and is typically assigned to the engineering and planning personnel responsible for the owner’s corrosion control program.

Information collected during the condition survey is linked to the physical items being evaluated. There must be a consistently applied organization to the facility or structure being evaluated. This organization is best accomplished before conducting the condition survey, although the results of the survey may require some adjustment to the originally conceived organization. There are typically three levels of detail involved in the organization and breakdown:

• Region

• Location/facility/structure

• Structural element/equipment

The primary goal is to make the conduct of the condition survey as simple as possible while collecting the necessary information.

This article is adapted from The Protective Coating User’s Handbook, Third Edition, Louis D. Vincent (Houston, TX: NACE International, 2010). The book is available from NACE as Item no. 37593.

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