Bridge Utilities Infrastructure News


A Primer to Cathodic Protection for Underground Piping Utilities

Posted by Edward Dill on Jul 13, 2018 9:00:00 AM



An Overview of Cathodic Protection

Cathodic protection is the process in which American Society of Mechanical Engineers (ASME) underground piping and propane tanks are protected from aggressive rust. (That is to say, some rusting is not necessarily harmful.) Cathodic protection addresses the steel disease (oxidation) by providing a protective layer to prevent further rusting. There exist two means in which cathodic protection for metal is achieved for underground piping: galvanized anodes (often referred to as sacrificial anodes) and impressed currents (typically referred to as impressed current cathodic protection).



Defining Cathodic Protection

In the smallest terms possible, cathodic protection is the prevention of corrosion.


Interesting fact: cathodic protection is actually the second measure in fortifying underground piping; steel coatings applied by manufacturers serve as the first.  


Why Cathodic Protection Is Important

Metal piping is responsible for innumerable daily constructs, yet they remain out of mind for those who are not tasked in their blueprinting, installation, and execution. Laypersons are unaware of their overwhelming dependency on reliable underground piping. Thankfully, we’re here to do the heavy lifting. Aptus’ 250 years of combined experience continues safeguarding communities and entire infrastructures from corrosion. (Cathodic protection is absolutely necessary in maintaining underground propane tanks, but that is outside the scope of this blog post.)


Unaddressed corrosion in complex underground piping systems foments holes in steel structures, which will eventually leak– potentially releasing harmful fumes and gases into nearby environments. That includes residential homes and bustling metropolitan business areas. Becoming familiarized with how the underbelly of cities, bridges, and mundane constructs interact with their environmental stressors and organic processes quickly reveals our overarching dependence upon the prevention of rust for smooth sailing!



Fighting the Steal Disease with Galvanized Anodes

At the bare essentials, an anode is an electrode existing in a polarized electrical device, through which current is able to flow. The current originates from an outside circuit. Cathodic protection with galvanized anodes typically revolves around high potential magnesium, magnesium alloy, and zinc. High potential anodes are utilized in sandy environments, where higher voltage rates are necessary. (1.75 volts to be exact.) Overall, magnesium's role in cathodic protection is to provide a continuous current of electrons to the entire surface area of interconnected pipes.

Zinc anodes service areas where underground piping systems encounter brackish groundwater.


How Galvanized Anodes & Electrons Protect Piping from Corrosion

Anodes prevent piping systems from oxidation. Anodes achieve this on a subatomic level through manipulation of high and low voltage relationships. In brief: anodes offer an artificial environment protecting metal from organically corroding. Throughout the process, electrons stop ions from oxidizing. When the entire piping system has achieved complete cathodic protection, the framework becomes a cathode.


A cathode is a negatively charged electrode, which allows electrons to pass through an electrical device.


Pros of Galvanized Anode Cathodic Protection

  • An economic solution to cathodic protection
  • Boasts low life-cycle cost to operate
  • Lasts for 50-70 years
  • Industry time tested (approximately 140 years)
  • Unaffected by UV radiation
  • Workers are less likely to damage during transport and installation
  • Limited maintenance costs
  • Environmentally sustainable
  • Simplicity

Cons of Galvanized Anode Cathodic Protection

  • Weighty for large projects
  • Somewhat limited operating conditions
  • Seawater drag
  • Limited current capacity
  • Ineffective in high resistance environments

Cathodic Protection with Impressed Currents

Whereas cathodic protection by way of galvanized anodes achieves anti-oxidation efforts in a closed knit environment, impressed current cathodic protection utilizes an outside power source to create the electrical current necessary to prevent rusting. This type of impressed current system is more efficient, as it offers protection over a longer period of time. This is due to an external power supplier, enabling voltage rates to rise considerably higher in comparison to the aforementioned anode cathodic protection. (Often referred to as galvanic or sacrificial cathodic protection systems.)


Pros of Impressed Current Cathodic Protection

  • Longer “shelf life” of anodes
  • Provides higher, more efficient, voltage
  • Unlimited output capacity
  • Ability to manipulate and manage system
  • Easy monitoring and troubleshooting
  • Longevity calculations are made possible
  • Cost effective
  • Easily installed
  • Flexibility

Cons of Impressed Current Cathodic Protection

  • Requires housing for external power source
  • Requires more maintenance for external source
  • Introduction of stray current damages
  • Nearby structures may be impacted by stray current corrosion
  • Demands experienced personnel and innovative design
  • Dependant upon constant power supply (power loss solutions must be ironed out)

Complications with Stray Current in Cathodic Protection

As an aside, stray current describes the reaction that happens when electricity–that is supposed to be dedicated to providing your underground piping with cathodic protection– finds itself in surrounding structures that were never supposed to receive its current. The discharge causes corrosion in unprotected sites.

Eargo, sometimes our endeavours to prevent corrosion in one site, causes that very thing somewhere unexpected. That’s why finding a company with time-tested experience in offering cathodic protection solutions and application is absolutely critical for long term success. Because who is going to become reliable for unforeseen damages to neighboring structures? You are.


Need Cathodic Protection?

Are you in a frantic craze looking for a cathodic protection contractor?


We’re here to tell you you’ve found one better.


Aptus is the apex of bridge utility design. We specialize in designing the nation’s utility infrastructure. We’d love to hear from you about your project.


At a glance, Aptus is the underbridge piping solution of the nation. We have installed more than 2,300 bridges across 43 states. But it’s not merely our order volume that compliments us, but our ability and dedication to adapt and craft innovative solutions for our clients. We can build the same bridge five times, no problem– but our strength lies in bringing individualized solutions to the great innovators of our nation.


If you’re still on the fence, here’s 3 Reasons to Go Aptus.


We pride ourselves on our history of excellence. Aptus is latin for connected, and that is who we are at the heart of our company. Our ultimate ends aren’t achieved until a turnkey solution for each unique challenge our clients face are not only met, but exceeded. We’re the all-in-one solution for complex hands-on piping systems. We like simple too. It helps us expand our portfolio.


Drop us a line or call (704) 598-5684

Topics: Pipeline Cathodic Protection, Cathodic Protection