Category Archives: Storage Tanks

[ARTICLE] Cathodic Protection Failure

Restore, replace, extend, or do nothing?

In the Autumn 2022 issue of Tanks and Terminals, MATCOR’s Ted Huck delves into four strategies you can take when your cathodic protection system is no longer working.


MATCOR provides industry-leading cathodic protection and AC mitigation solutions to tank and terminal operators around the globe.


If you need assistance with a cathodic protection assessment, please contact us. We will respond by phone or email within 24 hours. For immediate assistance, please call +1-215-348-2974.

Contact a Corrosion Expert

Is My Tank CP System Working Correctly?


Ted Huck, Director of Manufacturing and QA/QC at MATCOR, recently published an article in the summer edition of Tanks and Terminals Magazine titled “Understanding Cathodic Protection Systems.” He explains how to assess the performance of cathodic protection systems for above-ground storage tank bottoms (Tank CP Systems).

When asked to summarize these performance assessments, Mr. Huck commented, “Tanks are pretty easy to test, except for those rare occasions when they are not. At that point seek professional help.”

Read the full article.


Need information or a quote for MATCOR tank CP systems? Please contact us at the link below.

MATCOR Successfully Completes Tank CP Project In Mexico

JA Electronics explosion-proof rectifiers for tank CP project in Mexico.

MATCOR recently completed a significant tank CP project in the Mexican port city of Altamira along the Gulf of Mexico. The project consisted of design, detailed engineering, supplying materials, providing installation supervision, and commissioning and testing the systems upon completion of the installation for nine above-ground storage tanks.

Tank CP Project Utilizes Linear Anodes

The cathodic protection system utilized MATCOR’s SPL Linear Anode Concentric Ring tank system that consists of individual, factory assembled, and tested anode segments. This approach facilitates a simple installation that does not require cutting, splicing, or joining anode assemblies in the field. The anode rings utilize a redundant anode cable feed system that assures reliability. This cost-effective solution protects the bottom of tanks on projects across the United States and around the globe.

Explosion Proof Rectifiers

MATCOR also supplied customized explosion-proof oil-cooled rectifiers (pictured above) for each of these tanks from our sister company, JA Electronics. These rectifiers are used in Class 1 Div 2 hazardous areas. Additionally, cast aluminum Class 1 Div 2 junction boxes were also manufactured and supplied by JA Electronics.


Click below to get a quote for your tank CP project, or learn more about MATCOR’s cathodic protection solutions.

Corrosion Control for Water Treatment Facilities

We recently received an inquiry on our cathodic protection FAQ asking about “the best corrosion control protection for above-ground steel tanks treating wastewater.” Well, corrosion control for water treatment facilities is such an interesting and relevant topic that it warrants an expanded response, so here goes.

Wastewater treatment facilities generally have many tanks storing and processing wastewater through multiple treatment stages. These tanks and vessels are subject to corrosion, and there are a range of strategies to extend their service life.

Corrosion control for water treatment facilities' tanks and vessels

Corrosion Protection Strategies for Water Treatment Tanks and Vessels

These strategies fall into four broad categories: material selection, chemical treatment, coatings, and cathodic protection.

Wastewater Tank and Vessel Material Selection

From a material selection perspective, most wastewater treatment vessels are carbon steel. However, some chemical wastewater treatment facilities may require more “exotic” materials early in the treatment process due to the wastewater feed material.

Once the wastewater feed material has been treated and/or neutralized, the remaining process tanks and vessels are likely to be carbon steel construction.

Corrosion Protection via Chemical Treatment

The next broad category of corrosion control strategies is chemical treatment. While chemical treatment is an integral part of the wastewater process, specifically in terms of pH neutralization and chlorination processes, the chemical treatment performed during the treatment of wastewater is not typically intended to control corrosion.

One area where chemical treatment might be a viable corrosion control strategy is with the use of vapor corrosion inhibitors (VCIs) to protect the underside of steel storage tanks.

Coatings for Corrosion Control of Water Treatment Tanks and Vessels

The appropriate selection and application of coatings is a key corrosion control strategy for wastewater treatment facilities.

Coatings are particularly effective in protecting carbon steel structures including above ground piping, atmospheric external tank shells, wetted internal tank walls, submerged steel structures, and many other structures.

Coatings, however, are not perfect and they have a finite life. For structures that are easy to access, inspecting and re-coating are often the sole means applied to protect against corrosion.

Cathodic Protection

The final corrosion mitigation strategy that can be effectively employed to protect wastewater tanks and process vessels is the use of cathodic protection.

Cathodic protection can be used to protect bare steel structures, or in conjunction with coatings.

There are two basic types of cathodic protection, galvanic (often termed sacrificial) and impressed current. Some typical cathodic protection applications in wastewater treatment facilities include protecting the soil side bottoms of large above ground storage tanks and vessels, and protecting the internal wetted surfaces of tanks and process vessels including rotating equipment such as rakes and wiper arms.

MATCOR has extensive experience designing, supplying and installing cathodic protection systems for wastewater tanks and process equipment, including several proprietary impressed current anode systems that are especially well suited for these applications.


Have questions or need a quote for corrosion prevention materials or services? Contact us at the link below. For immediate assistance, please call +1-215-348-2974.

Contact a Corrosion Expert

MATCOR Featured in Tanks and Terminals

In the June 2021 issue of Tanks and Terminals, a quarterly supplement to Hydrocarbon Engineering, MATCOR’s Ted Huck discusses cathodic protection of terminal marine structures including docks, jetties, piers, seawalls and sheet pilings.

Protecting Marine Structures From Corrosion

The article includes a case story discussion from a Texas gulf coast facility using impressed current cathodic protection for a combi-wall structure (consisting of pipe piles and sheet walls.).

MATCOR provides industry leading cathodic protection and AC mitigation solutions to tank and terminal operators around the globe.

VCI for Tank Bottom Protection

The American Petroleum Institute (API) recently issued a landmark technical report regarding vapor corrosion inhibitor (VCI) use for storage tank bottom corrosion protection (API TR 655).

VCI has been promoted as a technology for use under above-ground storage tanks for the past decade. This effort recently received a big boost with the American Petroleum Institute’s publication of its long-awaited technical report on VCI.

Vapor corrosion inhibitor technology for tank bottom corrosion protection gets boost from API technical report.

API TR 655 Vapor Corrosion Inhibitors for Storage Tanks; First Edition; April 2021 provides the first set of guidelines for VCI issued by an internationally recognized non-governmental technical standards organization.

MATCOR has been an early adopter of VCI technology as we believe that it can be an important and effective component in a corrosion prevention program for tank bottoms. We have partnered with Zerust to be an authorized distributor and installer of VCI products for tank and other applications.

We are excited that API has led the way on recognizing VCI technology, and we would expect that other organizations–AMPP for one–will adopt similar guidelines and recommendations.

For a more detailed review of the technical report, visit our VCI partner company Zerust’s summary at the link below:

Summary of API’s Vapor Corrosion Inhibitor Use for Storage Tank Bottom Protection API TR-655


To get in touch with our team of cathodic protection experts for more information, to ask a question or get a quote, please click below. We will respond by phone or email within 24 hours. For immediate assistance, please call +1-215-348-2974.

Contact a Corrosion Expert

Horizontal Directional Drilling for a Middle East Tank Retrofit

In a recent Tanks & Terminals article, Ted Huck discusses a tank cathodic protection retrofit project in the Middle East utilizing horizontal directional drilling technology.

Existing tanks pose several challenges that must be considered when looking to install cathodic protection, since access directly below the tank is not readily available.

Originally constructed in 1995, the original design of this critical service ethylene storage tank included a cathodic protection system to protect the external tank bottom in contact with the ground. Over time, the system stopped providing enough current to meet NACE criteria for the control of corrosion. 

Discrete Anodes Along the Tank Perimeter Not Satisfactory

The first retrofit cathodic protection system consisted of installing discreet anodes around the perimeter of the tank. While relatively easy to install, this method of retrofit installation often struggles to drive current to the full tank bottom. The results were not satisfactory so another method was needed.

Linear Anodes Installed Using Horizontal Directional Drilling

MATCOR had proposed an alternate approach, successfully being performed in the US but not tried previously in the Middle East. It involves the installation of multiple strings of linear anodes directly below the tank using horizontal directional drilling (HDD) technology. By drilling under the tank, it is possible to install anodes spanning the entire length of the tank. This method also allows for a testing device to measure the effectiveness of the cathodic protection system.

Click below to read the full article regarding this tank retrofit cathodic protection system, installed successfully in December 2019.


If you have questions, or for information on MATCOR’s above ground storage tank cathodic protection solutions, please contact us at the link below.

Contact a Corrosion Expert

Better Tank Cathodic Protection

Looking for a better tank cathodic protection system?

Find our article in the April 2020 Storage Terminals Magazine. “No More Gridlock—Take the Ring Route” is a comparison of grid anode systems vs concentric ring systems for tank bottom cathodic protection.

Cathodic Protection of the external tank bottom for large diameter above ground storage tanks has been adopted as good engineering practice around the world.

Unfortunately, many existing grid anode systems have experienced premature failures, resulting in excessive tank bottom corrosion and costly replacement.

A recent MATCOR article published in Storage Terminals Magazine provides an overview of these grid CP systems and an alternative concentric ring linear anode system (link to the full article below). Here are just a few key points:

Grid Tank Anode Systems

  • Consist of field assembled MMO ribbon anodes and titanium conductor bars
  • Require flawless design and installation
  • Subject to poor welding and other concerns
  • Failures can be catastrophic

Concentric Ring Linear Anode System

  • Factory assembled—no field cutting or splicing required
  • Easy, fast and reliable installation
  • Coke backfilled sock protects the anode
  • Redundant—each ring segment has two feeds
  • Long life compared to the grid systems of the 1990s

If you have questions, or for information on MATCOR’s above ground storage tank cathodic protection solutions, please contact us at the link below.

Contact a Corrosion Expert

Does Cathodic Protection Cause a Tank Bottom to Dry Out?

Does Cathodic Protection Dry the Tank Bottom?
Will your CP System dry out the sand bedding of your tanks?

A client recently raised the concern about the cathodic protection reaction causing a drying out of the sand under a large diameter above ground storage tank.  This is a very interesting question.  We recently developed a stoichiometric analysis to assess the cathodic protection carbon footprint of a deep anode system by calculating the amount of carbon dioxide produced. The same methodology can be used to assess the risk of drying out of the tank bottom.

Assumptions

For this analysis, let’s assume a typical 150 ft diameter above ground storage tank with a bare tank bottom and a 1-foot sand bed resting atop a non-permeable liner.  Based on a common design criteria of 2 mA/ft2 of bare surface area, this tank would nominally require a total of 17.7 amperes of current. 

How much water does a cathodic protection system consume?

For every 2 electrons generated, one H2O molecule is required.  One amp-year is equal to 3.1536 x 107 amp seconds or coulombs.  One Faraday or 96.487 coulombs is equal to one mole of electrons therefore, one amp-year is equal to 326.84 moles of electrons.  With the 2 to 1 ratio of electrons to H2O molecules that means that for every mole of electrons, 0.50 moles of H2O are generated.  H2O has a molar mass of 18.0 g/mol so for each amp year a total mass of 2,941.6 grams of H2O is generated – that is approximately 0.78 gallons of water per amp year. 

For our 17.7 ampere, 150 ft diameter tank anode system, that would mean 13.8 gallons of water is consumed as part of the cathodic protection reaction each year.  Assuming that there is no new water being added into the tank foundation (a perfect chime seal and a completely non-permeable liner), then over a 30-year operating life the CP system would consume a little more than 400 gallons of water. While that might seem like a lot of water consumption, what is the percentage of drying out that is occurring with the sand over that time frame?

Will the Tank Bottom Dry Out?

Well, typical sand has a bulk density of approximately 100 lb/cubic foot and the typical moisture content for commercial sand is between 2% and 6%.  For purposes of this exercise, let’s assume that the moisture content is on the low end at 2%.  This means that there are approximately 2 lbs of sand per cubic foot.  A 150 ft diameter tank has 17,671 cubic feet of sand bedding which equates to 35,342 lbs of water or about 4,241 gallons of water.  So, if no new water is added over the thirty-year operating life, the typical CP system will consume about 10% of the sand moisture for very dry sand.  

Conclusion

Given our assumptions and calculations, it does not appear that significant sand drying will occur due to water consumption.

Another Consideration: Electro-osmotic Drying

This analysis does not consider the effect known as electro-osmosis.  Electro-osmotic drying is a process that is used in the civil engineering world to dewater sludges by creating a DC electrical flow – the flow of electrons pulls polar water molecules away from the anode.  For CP applications, this is generally not considered to have a significant impact except where there are very high current densities at the anode – for example some deep anode systems operating at very high output rates in certain soil formations. For tanks, this is not considered an issue.


If you have other technical questions, or for information on MATCOR’s above ground storage tank cathodic protection solutions, please contact us at the link below.

Contact a Corrosion Expert

Get News from MATCOR

Sign Up for Our Newsletter

    I understand my information will be stored securely for the sole purpose of conducting business with MATCOR, Inc. I agree to receive future email communication and understand that I may opt out at any time. View our Privacy Policy.
  • This field is for validation purposes and should be left unchanged.