for previous articles, visit the
Infrastructure Preservation News archives
and V&A's web site at www.vaengr.com

Creating a Corrosion Control Master Plan

With a well-thought-out corrosion control plan, water and wastewater plant owners can stretch their maintenance dollars, prevent unnecessary repairs, and extend the service life of pipes and structures.

The challenge
Over the past 29 years, V&A’s corrosion engineering department has performed hundreds of condition assessments on water and wastewater treatment plants across the U.S. Strikingly, many of these plants, though designed to have the most advanced treatment technologies available, have no corrosion control system, or have a rudimentary one at best. Yet this single, easily affordable protection is one of the most important measures the plant owners could take to protect their investment. Virtually every element of a water or wastewater treatment plant is potentially vulnerable to corrosion damage, which can take many different forms. Some typical examples of such corrosion-related asset deterioration are shown these photos.

Photo 1. Graphitization of buried ductile iron pipe in corrosive soil.	Photo 2. Wastewater leaking out between the PVC liner and corroded concrete in a clarifier.
Photo 3. Advanced hydrogen sulfide attack has exposed the reinforcing bar in a gravity sewer pipe.	Photo 4. Corrosion of a vent atop a water storage tank.

Protective systems
All of the damage shown in these photos could have been prevented during the planning and design phase. A polyurethane coating on the exterior of the ductile iron pipe (Photo.1), together with a cathodic protection system, would have prevented the rapid deterioration of the pipe. The damage shown in Photos 2 and 3 could have been prevented with the use of an epoxy or a PVC liner. Similarly, the corrosion seen on the vent of the water storage tank in Photo 4 could have been slowed or prevented by using an aliphatic urethane coating system formulated to withstand humidity and sunlight. In our experience, most or (more commonly) all of the following measures should be considered necessary for adequate corrosion control in a water or wastewater system:

• A protective coating system on all concrete or metal structures that will be exposed to harsh chemicals, gases, or wastewater.
• A cathodic protection system in the plant’s design, including monitoring test stations, impressed current (rectifier) systems, insulating flanges, and galvanic (sacrificial) anode systems.
• An ongoing inspection program that includes a condition assessment of all system components, especially sewer siphons, clarifiers, drinking water storage tanks, digesters, sedimentation basins, and buried pipelines.
• A corrosion inhibitor monitoring system to protect piping from internal corrosion.
  
  

Planning a system
Existing water or wastewater plants can benefit significantly from having a corrosion control master plan to better protect all pipelines and structures. There are several ways to begin implementing such a program. Typically, implementation includes:

Inventory all buried metallic piping, to ensure (1) that any existing cathodic protection is working properly and (2) that all the piping is isolated from building structures and other pipes.

Collect soil and atmospheric samples to evaluate the corrosivity of the environment surrounding the concrete structures or buried pipelines.

Based on the data collected during the inventory and sampling, develop a plan to monitor the condition of buried pipelines with the installation of new test stations and insulating flanges.

After the test stations are installed and monitored, the data would indicate the level of cathodic protection needed for different groups of piping systems. This would be followed with installation of an impressed-current or galvanic cathodic protection system. The piping would be grouped together based on several criteria, including
• pipe material,
• size of piping,
• existing shorts to other structures, and
• ease of installation.


Prepare plans and specifications for the installation of test stations and CP systems.

Assist contractors during bidding.

Implement and monitor the corrosion control plan, in partnership with the owner’s staff or operations and maintenance (O&M) crew.

For existing concrete structures at water and wastewater treatment plants the implementation of a corrosion control plan will include the following:

Perform a condition assessment of all concrete structures exposed to harsh chemicals, gases or wastewater.

Identify and prioritize all those structures that are in dire need of repair or replacement, based on the results of the condition assessment.

Prepare plans and specifications for the repair or replacement of damaged concrete structures.

Provide assistance to contractors during bidding.

By implementing a corrosion control plan, the service life of a structure or pipe could be extended and would prevent many unforeseen repairs. In the end, implementing a corrosion control plan will ensure that an owner’s maintenance dollars are well spent. If you would like more information on this subject please contact us at 510-903-6600.