Cheap and abundant Marcellus Shale gas derived from US fracking technology helps to drive competitiveness for a wide range of industries in the United States. This is especially true for the US Steel industry, and MATCOR’s recent project in Western Pennsylvania in the rolling hills of the Monongahela Valley is a great example of this.
Nestled on a hilltop 250 feet above the valley is US Steel’s Mon Valley Works–Irvin Plant. This hot strip mill in the Pittsburgh West Mifflin suburbs first opened in 1938. The hilltop site required more than 4.4 million cubic yards of earth to be moved, more than any other project other than the Panama Canal. In May of 2019, US Steel announced plans to invest $1 billion dollars at the site to expand it and to build a cogeneration power facility expected to be operational by 2022.
MATCOR was selected by US Steel to install, commission and test an impressed current cathodic protection system to protect the critical coke oven gas (COG) product pipelines mixed at the West Mifflin COG facility. The coke oven gas is a mixture of commercial natural gas and recovered waste coke gas. This blending of natural gas with recovered gas reduces costs and improves US Steel’s energy efficiency. The pipeline, affectionately called the Green Monster, traverses the valley feeding various facilities. Mostly above grade, the pipeline goes below grade in numerous locations.
MATCOR’s MMP 3605 mixed metal oxide based canister anodes were selected as the new cathodic protection system anodes to protect the buried piping. Fifteen anodes were installed in individual 20-foot depth augered holes and connected to a #2 HMWPE buried header cable requiring approximately 1500 linear feet of trenching. The project included site specific safety training, regular coordination with site personnel and site restoration (seed, straw and fertilizer) after completion of the installation.
The project was a tremendous success and MATCOR is proud to have been able to partner with US Steel for their buried pipe corrosion protection.
Have questions or need a quote for cathodic protection materials or services? Contact us at the link below. For immediate assistance, please call +1-215-348-2974.
MATCOR’s proprietary deep anode system is a cost-effective approach to installing deep anodes.
Recently a customer asked MATCOR to bid the installation of multiple deep anode systems, each consisting of 15 high silicon cast iron anodes to be installed in 350-ft. deep holes. MATCOR provided an alternate proposal based on our proprietary Durammo® system.
2 Major Benefits of Durammo
It eliminates the need for a junction box
It requires a lot less cable due to its being a continuous anode system with only two primary cables
Meaningful Cost Savings
When you are looking at 15 individual anodes with hundreds of feet of dual insulated HMWPE/Kynar® or Halar® (pick your preferred fluorinated polymer – they are very similar in their chemical resistance and are both suitable for deep anode installations), the cabling costs are significant as is the cost of a suitably sized junction box. Multiply these savings over several sites and it can lead to a meaningful costs savings over the typical conventional anode installation.
Our client took advantage of the cost savings for the Durammo and awarded MATCOR the installation work and used the cost savings to have MATCOR repair, replace and add additional test stations instead of paying for a lot of additional cable and junction boxes. The Durammo cost savings allowed the operator to expand the scope of work doing more with the monies budgeted on the project.
Talk to your MATCOR representative to see how the Durammo can allow you to get more done with your limited CP budget monies.
To get in touch with our team of 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.
Wait, I still have stuff that needs to be completed this year!
This is a sentiment that many of us feel. It’s been a crazy year the likes of which we have never seen before and hopefully we will not see again.
But before we turn the page on 2020, many of our clients have expressed to MATCOR that they still have projects that were supposed to be completed in 2020—budgeted projects that still need to be completed this year. Between the lockdowns and the uncertainty over oil prices, too many projects were delayed or slow to get started. Now that we are several weeks into the fourth quarter and the weather is starting to turn, the working daylight hours are winnowing, the holidays are approaching, and the demand for cathodic protection installations is quickly filling up the available capacity in the market place. There are only so many hours left in this year.
MATCOR is here to help.
We are working as hard as we can to satisfy as many customers as possible with our remaining capacity, and we are also encouraging customers to consider getting an early start to their 2021 construction project schedule.
Typically, January and February are slow construction months. In part this is because of weather issues, but often it is a budget cycle issue – clients are still finalizing their budgets, project teams are just getting back from the holiday season, and bid packages are being developed to be issued in February or March for a lot of CP construction work. We expect 2021 will be a very busy year as owners and operators catch up on work that was pushed out, could not be completed in 2020, and begin to comply with new PHMSA Mega Rule requirements.
We encourage all customers to consider getting started early – MATCOR is available to work with you. If you have 2020 budget money but are not able to get the work completed in 2020, consider purchasing the materials with your 2020 monies and completing the installations in early 2021. MATCOR can work with you to procure and store the materials and to plan an early first quarter installation.
Contact your MATCOR representative at the link below to discuss options for work that has been delayed or that needs to be done quickly. We will do our best to support you.
Josh Johnston, MATCOR’s director of sales, wanted to share a recent conversion of a new customer to the growing list of satisfied Durammo Deep Anode System users. As Josh explained, “the Durammo is a salesman’s dream product. It offers our customers an innovative product that has an amazing track record. Its design makes it safer and easier to install because it comes preassembled ready to immediately lower down the hole.”
A complete description of the Durammo deep anode system is available here.
As Josh continued, “The hardest part about selling the Durammo, is that it is different than what they have used and what others are offering. There is a certain leap of faith that we ask customers to take when trying something different. I can explain to them that it is less expensive, has a longer operating life, is safer and easier to install, that several thousands of these are installed across the country and around the world, some with more than 20 years in service. It all sounds great, but it is different. That is my job, to convince people to do something different.”
One such company is Enerfin Resources Company, a midstream company operating natural gas and crude oil field services assets in Oklahoma, Texas and Louisiana. MATCOR met with them in the Fall of 2019 and explained to the Enerfin team the benefits of the Durammo deep anode system. As Josh noted, “Enerfin was willing to try this “new to them” technology, based on the value we offered.”
In March, MATCOR installed three of the Durammo systems for Enerfin. Tony Gustin, Project Development & Construction Manager noted, “the installation of these systems was very professional and the factory assembled system dropped in place as easy as advertised. We are sold on this product and look forward to using MATCOR and the Durammo system on many future projects.”
If you are ready to try something better, but different for your next deep anode system project, contact MATCOR and we would be happy to help you take the next step.
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.
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.
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.
This article explores the carbon footprint of cathodic protection deep anode systems and compares it to that of a typical passenger car.
Deep Anode Systems
Deep Anode Systems are commonly used throughout the CP industry as a cost-effective means to discharge significant amounts of current to protect pipelines over long distances or large structures in a small area. One of the common components in a deep anode system design is the vent pipe.
The deep anode system vent pipe serves two important related functions:
To prevent gas blockage that will impede the
operation of the anode system
Prevents the accumulation of chlorine
concentrations where chlorides are available
Both issues are directly related to the electro-chemical reactions that occur at the anode to coke backfill, and coke backfill to earth interfaces.
There are two basic types of anodes used in deep anode systems—conventional “massive” anodes, and dimensionally stable anodes.
The conventional “massive” anodes are those anodes that consume as part of the electro-chemical reaction and as such their mass is critical in determining the system’s performance life. The dimensionally stable anodes, typically Mixed Metal Oxide (MMO), are catalytic in nature and do not consume as part of the anodic reaction.
Cathodic Protection Reactions
The primary cathodic protection reactions all involve generating gas:
In a properly functioning deep anode system, the gases that occur from these reactions predominantly involve the coke backfill creating carbon monoxide and carbon dioxide. If chlorides are present, some percentage of chlorine gas will also be generated.
The Importance of Venting the Deep Anode System
The gases generated in the coke column typically do not rapidly diffuse into the earth around the coke column and thus will build up. These gases are not electrically conductive and once enough gas builds up around the anode, then the anode can no longer effectively discharge current—a phenomenon known as gas blockage. If Chlorides are present, the chlorine gas reacts with water to create hydrochloric and hypochlorous acids that can attack the cable insulation and cause permanent damage. This is why it is important to properly vent these gases that are a part of the electro-chemical reaction that must occur for CP to function.
What’s the Carbon Footprint?
Given that deep anode systems generate gas, an interesting, although not commonly asked question, is how much carbon dioxide a typical deep anode system generates—in other words, what is the carbon footprint of a deep anode cathodic protection system.
With a few worst-case assumptions and a little stoichiometric chemistry analysis we can answer this question. Assuming all the reactions are generating carbon dioxide and there is no oxygen generation, then for every 4 electrons generated, one CO2 molecule is generated.
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 4 to 1 ratio of electrons to CO2, that means that for every mole of electrons, 0.25 moles of CO2 are generated. CO2 has a molar mass of 44.01 g/mol, so for each amp year a total mass of 3,596 grams of CO2 is generated.
For a nominal 50 amp anode system, that would mean a maximum generation of 180 kg of CO2 per year if CO2 was the only gas generated.
How much CO2 is 180 kg/year?
The EPA estimates that the typical passenger vehicle generates 4,600 kg of CO2 per year.
Therefore, your 50 amp deep anode system generates about 4%—or just 1/25th—of what a typical passenger car generates annually.
If you have other technical questions, or for information on MATCOR’s deep anode cathodic protection solutions, please contact us at the link below.
MATCOR is a leading manufacturer of impressed current sled anode systems and as such we tend to get asked a lot of questions about sled anodes. Here are some frequently asked questions:
Does it matter whether sled anodes are to be installed in seawater, brackish water or freshwater? What if the water salinity varies with the season or with tidal action?
These are two related questions, and both have to do with the conductivity (or resistivity which is merely the inverse of conductivity) of the water where the anodes will be located. The conductivity of the water plays a critical role in determining the overall system resistance and current output of the system. For freshwater locations, the relatively low water conductivity requires a significant quantity of anodes to keep the overall system resistance down. In those instances, a sled anode may not be the best design option as sled anodes are most cost effective in brackish or saltwater environments. For environments where the conductivity can vary seasonally or with the tides, such as estuaries or tidal river boundaries, special consideration may be required such as constant current or auto-potential controlled power supplies.
Why would we use impressed current sled anodes as opposed to galvanic anodes?
Depending on the application, there are compelling reasons for the use of each type of system. Galvanic anodes do not require an external power supply, are less subject to interference issues, and can be closely coupled directly to the structure. The impressed current sled anodes can greatly simplify installation, reduce overall costs, typically have a longer life, and can produce a lot more current from a lot fewer anodes. The choice of anode type is very much a site-specific consideration requiring a proper engineering evaluation during the design phase.
Are there any specific concerns with marine wildlife when evaluating cathodic protection systems?
Marine wildlife is generally unaffected by the presence of a cathodic protection system. Cathodic protection systems have been used in commercial aquariums and fish hatcheries without any impact on the marine life. At the structure, cathodic protection can result in a localized environment that reduces or inhibits the growth of barnacles while changes in the pH at the structure’s surface encourage the growth of calcareous deposits which reduce the current requirements and provide a form of protective coating for the steel structure.
The MATCOR sled anodes utilize a wooden base – are there any concerns with the deterioration of the wooden base releasing in chunks of wood that could damage intake structures?
We have not experienced any such problems – the wooden base is designed to sink into the mud along the sea floor and provide an anchor. Wood holds up very well in this environment; however, over time the wood will slowly become food for cellulose processing bacteria and eventually will slowly be degraded. This process is a natural process and occurs over a long period of time. There is no expectation that the wood base would break into pieces that could damage an intake structure. MATCOR can provide an inert non-metallic plastic base that would be like wood but not subject to natural biodegradation.
How do you protect the cabling from the Sled Anode back to the system rectifier?
MATCOR utilizes an HMWPE cable that has a very robust exterior jacket that is suitable for direct burial in soil or water environments. The cable is housed inside a 1” diameter flexible drilled PE pipe that provides mechanical protection for the cabling. We recommend the use of concrete weights to secure the cable along the seafloor. The drilled PE pipe holes facilitate the cabling sinking into the seafloor mud providing additional protection for the cabling.
What about dredging operations?
For locations that are subject to occasional periodic dredging operations every few years or so, MATCOR can provide a locator float and lifting lugs to allow for the anodes to be removed prior to dredging operations. If the frequency of the dredging operations is such that this would be a regular occurrence (multiple times per year), then consideration should be given to alternate designs that would not require anode removal on regular basis.
For information on MATCOR’s Sea-Bottom Marine Anode Sleds or for assistance with marine near shore cathodic protection system design, please contact us at the link below.
A common cathodic protection system approach is the use of a shallow horizontal anode bed. These are typically defined as an anode system consisting of a series of multiple individual anodes installed either vertically or horizontally at a depth of less than 15m (50ft) and connected to a single power source. These are particularly effective in areas where drilling deep anode beds is not feasible or practical.
The typical anode used in shallow anode bed applications is an impressed current anode. These can be high silicon cast iron, graphite anodes or mixed metal oxide tubular anodes. The anodes may be pre-packaged in a canister filled with coke backfill, or they can be installed in a vertically drilled/augured hole or a continuous horizontal trench with backfill installed around the bare anode. The anodes can be installed in parallel to a common header cable or can have individual leads all routed to a cathodic protection junction box and connected in parallel inside the junction box.
A New Approach: Continuous Linear Anodes
Another approach that is gaining acceptance in the corrosion industry is the use of a single continuous linear anode as an alternative to multiple individual discreet anodes that are field connected to form an anode bed. There are several advantages to using a single continuous linear anode to create a shallow horizontal anode bed:
Advantages of linear anodes for shallow horizontal anode beds
Ease of installation The use of a single continuous linear anode assembly can significantly reduce installation time by eliminating numerous field splice connections of multiple individual anodes to a header cable.
Reliability The entire linear anode assembly is factory manufactured and tested with internal factory connections that are more reliable than a field connection. The assembly is designed with an internal header cable for redundancy and can be manufactured with an integral external return header cable, eliminating all field splicing and connections.
HDD Installation The use of a linear anode for shallow anode bed design allows for the use of HDD (horizontal directional drilling) to install the continuous anode assembly. This can significantly minimize the installation footprint and greatly reduce installation time and costs. This also allows for a deeper installation to facilitate locations where surface activities such as deep tilling farming operations might preclude a shallower anode system installation.
Cost Effectiveness The use of linear anodes can be extremely cost effective, resulting in a much lower cost installation. This is especially true when considering the overall cost per amp year given the longer design life of mixed metal oxide based linear anode systems.
MATCOR has extensive experience designing and installing shallow horizontal anode beds, including the use of our HDD installation crews and state-of-the-art equipment to minimize surface impact in sensitive areas.
Contact us at the link below to find out if a linear anode cathodic protection system is right for your application.
Last month, MATCOR successfully completed the first ever HDD tank cathodic protection system installation in the Middle East, utilizing a replaceable anode system.
Background—Initial Recommendation for HDD Cathodic Protection System
Equate Petrochemicals is one of the world’s largest producers of Ethylene Glycol. They initially contacted MATCOR in 2012 to discuss options for cathodic protection on a critical service Ethylene storage tank at their flagship Kuwait petrochemical facility. This tank was originally constructed in 1995, and the initial CP system installed with the tank was no longer providing sufficient current to achieve NACE Criteria. At the time, MATCOR suggested installing anodes directly under the tank using horizontal directional drilling technology. The plant’s engineering and operations team had significant reservations about this approach. The tank was critical to the plant’s operation and could not be taken out of service. Should the HDD operations result in damage to the structural integrity of the tank, the results would be catastrophic.
Perimeter Anodes—An (Unsuccessful) Alternative Approach
As a result of Equate’s concerns in 2012, they attempted an alternate approach, suggested by others, using perimeter anodes. Discreet anodes were installed offset around the perimeter of the tank—thus avoiding any possible risk to the tank during the anode installation. The use of perimeter anodes around larger diameter tanks is generally not a good idea. This is because it is very difficult to drive current to the center area of the tank, often resulting in adequate protection levels only for the outer edges of the tank bottom. For the Ethylene Storage Tank, the presence of heating pipes below the tank bottom only exacerbated the current distribution challenges. Ultimately, the results were not satisfactory.
In 2018, the plant engineering team reached back out to MATCOR to discuss our HDD solutions.
Replaceable Anode System Solution
MATCOR provided the plant with a detailed proposal to design and install a complete cathodic protection system using MATCOR’s Replaceable Tank Anode system. The RTA system is based on installing MATCOR SPL linear anode assemblies in a series of parallel slotted PVC pipes that have coke backfill pneumatically blown into the PVC pipe as part of the anode system installation. In addition to the linear anode segments and coke backfill, the slotted PVC pipes have a venting system to allow gases produced during the cathodic protection reaction to vent. This prevents gas buildup and blockage inside the PVC anode pipe.
One of the key advantages of the RTA system is that once the PVC tubes are installed, it is possible to flush out the anode assemblies and coke backfill should the anode assemblies fail and/or they are at the end of their design life making this a replaceable anode system that will assure cathodic protection for the entire service life of the tank.
Additionally, a slotted Reference Cell Tube would be installed to allow for two calibrated fixed cathodic protection reference electrodes to be inserted for full polarized and non-polarized potential measurements across the entire tank bottom. This would allow for testing of the CP system with calibrated reference electrodes for the life of the tank.
Experienced HDD Installation—Assuring a Safe Installation
While the plant conceptually agreed with MATCOR’s solution from a technical perspective, there remained a significant concern within the plant’s operation and safety groups about drilling under this critical service tank and the possibility of a catastrophic event should the drill head drift up to the tank bottom. MATCOR put together a thorough installation procedure including detailed information on the sophisticated drill head tracking systems being utilized to assure that the drill head location was being continuously monitored throughout the bore. Utilizing an experienced local HDD drilling sub-contractor, MATCOR deputed its senior HDD installation drilling supervisor to Kuwait for the installation. Our Senior HDD Drilling Supervisor has completed hundreds of tank HDD installations in the United States and his on-site presence, along with the advanced electronic tracking package being used, assured that each bore went as planned.
Replaceable Anode System Installation Complete!
In December of 2019, MATCOR, working with our local Kuwaiti sub-contractor and the client’s engineering, construction and safety teams, successfully completed the installation of the replaceable anode system. The initial commissioning results showed that the anodes were installed properly. Each anode was distributing current as expected, and the polarization levels were meeting appropriate NACE criteria. The system has been left to operate and fully polarize. A subsequent visit by MATCOR’s technical team is scheduled in early 2020 to make final adjustments to the anode system current output and to confirm that the system continues to meet NACE criteria.
MATCOR’s successful installation in Kuwait of a horizontal directional bored CP system under an existing critical service tank is a first for the Middle East Region. The innovative MATCOR design, combined with the technical knowledge and operational expertise, makes this an interesting and viable option for other tank owner/operators worldwide to consider for their existing tanks with CP systems that are not performing properly.
To get in touch with our team of cathodic protection and AC mitigation 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.
Are Vapor Corrosion Inhibitors Magic Dust or a Viable Corrosion Prevention Tool?
This article is intended to provide a basic primer on vapor corrosion inhibitors for use in corrosion prevention for above ground storage tanks and address where this technology stands.
There has been a significant effort within the oil and gas world to either promote or repudiate the use of Vapor Corrosion Inhibitors (VCIs) for tank bottom plate corrosion control. As a leader in the above ground storage tank corrosion control industry, MATCOR has partnered with Zerust® Oil & Gas to make VCI options available to our customers that are interested in applying this technology as part of their corrosion mitigation approach.
How Vapor Corrosion Inhibitors Work – Video Courtesy Zerust® Oil & Gas
What are vapor corrosion inhibitors and how do they prevent corrosion?
VCIs are chemical compounds that are released into a confined space, such as the underside of a tank bottom, and diffused through the sand pad material to reach the metal surface. These compounds are adsorbed onto the metal surface forming a strong bond that promotes and maintains a passive oxide layer on the metal and blocks other contaminant molecules from reaching the surface.
Are VCIs a non-permanent solution?
Corrosion protection using VCIs requires sufficient chemical concentration to thoroughly diffuse across the entire tank bottom surface area. The VCI has a finite life, after which it ceases to remain active. When this occurs, further chemical is required to replenish the spent VCI. The frequency of VCI replacement will vary depending a range of factors:
The rate of leakage through the tank chime
The operating temperature of the tank
The sand properties
The amount of chemical initially applied
As VCI technology is still in the early phase of adoption, the typical replenishment frequency remains one of the big unknowns. A conservative estimate would be a minimum of 3-5 years’ service life before replenishment although a least one source has reported upwards of 15 years of effectiveness.
How is VCI applied initially for above ground storage tanks?
There are a variety of application technologies depending on the application and whether the tank is new construction, existing tank during inspection, a tank that is in-service or a double floor tank. Other considerations include the substrate material or concrete pad. The VCI chemical can be provided in a powder or liquid form. Whatever system is utilized to deploy the VCI, consideration should be given to how it will be replenished over the life of the tank.
Can vapor corrosion inhibitors be used in lieu of cathodic protection?
Practically speaking, most tank operators are not looking to replace cathodic protection but are considering VCI as a supplement to cathodic protection or as a short-term solution for inadequate or depleted CP systems until a replacement CP system can be installed.
Can VCI be used as a complement to cathodic protection?
This is where VCI provides an exciting opportunity to supplement cathodic protection. While cathodic protection has a proven track record in corrosion prevention for tank bottoms, there are limits to the effectiveness of cathodic protection. Cathodic protection only works when the tank bottom is in intimate contact with the sand bottom. Localized corrosion can occur wherever there are air gaps under the tank bottom. These can occur due to flexing of the tank bottom, imperfections in the plate steel, lapping of the plate steel, poor compaction of the sand bottom, presence of aggregate or non-conductive materials such as asphalt or oil, and at crevices in the tank ring wall. These are all areas where cathodic protection may not be effective and the proper application of VCI would be an excellent means of providing corrosion protection in these localized areas. Cathodic protection and vapor corrosion inhibitors are symbiotic. CP current distribution has been shown to improve in the presence of VCI.
How do I monitor that the VCI is working?
When applying VCI to a tank bottom, coupons, ER probes or UT probes installed under the tank are used to measure the effectiveness of the VCI and to alert the owner when the VCI requires replenishment. One of the concerns with using ER probes to measure corrosion rates under tanks is that ER probes provide an average corrosion rate and not localized pitting rates. It is understood that pitting corrosion is the dominant factor in tank bottom corrosion related failures and pitting rates can be significantly higher than average corrosion rates. There is a distinct correlation between average corrosion rates and pitting corrosion rates and the ER probes can be used to infer changes in the pitting rates.
Where do vapor corrosion inhibitors stand with industry standards and regulations?
According to API 651, there are several situations where CP is not recommended for specific tank foundation designs. In some of these designs, PHMSA recognizes that CP is not feasible. In these cases, VCI can be a viable option. API 2610, the Tanks and Terminals standard outlines the use of VCI for tank bottoms in section 12.5. API 651, the CP standard, is being updated currently and VCI is being included as an option in this document. The State of Florida has identified that VCI can be used in tandem with CP or a standalone solution, for more than 6 years. NACE is currently working on publishing a standard “NACE TG543”, which is a comprehensive document on the application of VCI under tank floors. PHMSA is currently reviewing Special Permit requests for the use of VCI without a functioning CP system. If a non-regulated tank’s CP system is not meeting criteria, or has depleted, but the tank is still a few years from its next inspection, VCI can be applied to protect the floor until CP system repairs can be economically accomplished.
What independent published studies exist supporting VCI?
A 2018 study published by PRCI provides the strongest validation of the effectiveness of VCI and concluded that:
VCIs were found to be effective in mitigating pitting of steel exposed to corrosive sand but was not as effective as CP for reducing pitting corrosion. The study confirmed the importance of using the manufacturer’s recommended concentrations, as low levels of VCI was found to be ineffective.
ER Probes can be used to monitor the efficacy of VCIs
VCIs are compatible with impressed current cathodic protection; however, VCIs change the native potential of the steel and this must be considered when selecting CP criteria in accordance with NACE SP0193
In conclusion, the application of VCI is a viable tool in our corrosion tool box that should be considered in conjunction with cathodic protection for critical service applications and as a standalone solution in some applications.
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.