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Closed System Water Treatment Problems: Corrosion

Posted by Richard Cannon on

Some of the leading conditions that can cause problems in closed systems are:

Leaks. Water loss, either through leaks or intentional releases, will drain away any chemical corrosion protection and introduce fresh, oxygen rich, water. When fresh water enters a closed system the dissolved oxygen will react with metals such as iron and copper. When oxygen reacts with iron it forms iron oxide (rust) that can expand thethickness of the iron by up to 20 times.

Exposure to atmospheric oxygen. Approximately 20% of the atmosphere is oxygen. If the water in a closed system with an open tank is exposed to the atmosphere, oxygen can easily enter the system and accelerate corrosion. In addition to closed system deposit and corrosion inhibitors, adding biocides to control biological growth is advised.


Corrosion increases with stagnation. In closed systems where the water remains stagnant for long periods of time there is an increase in corrosion. It is better to circulate the water and maintain a protective chemical concentration in all sections of a closed system. Periodically running the circulation pumps at least weekly and maintaining treatment levels will help reduce the corrosion.


Deposition. Corrosion deposits in one area can migrate to other areas and plug pipes, control valves and heat exchangers. Consider chemical cleaning (see below) and filtering the water.

Corrosion deposits can cause wear and tear on seals and pumps.


Moderate Cleaning Process:

  1. Add a borate nitrite treatment to 1500 ppm as sodium nitrite and test the water.
  2. Circulate the water for at least 24-hours.
  3. Start a bleed on the closed system and flush the water to sanitary sewer while running the circulation pumps until the nitrite level drops to 500 – 700 ppm as sodium nitrite. Testing can be performed by using our Nitrite Test Kit CNTK3300-Z
  4. Repeat the process by adding the borate again and re-flushing after 24-hours.

Filter in addition to chemical cleaning.

  1. Install a 1 to 5 micron filter on a bypass to the circulation pump and check the filter daily. Replace or clean the filters when noticeably fouled. We recommend the Vector 7 Gallon Filter-Feeder with 5 micron filter sock. 
  2. If there is an open tank, suction out any deposits that may be deposited on the bottom of the tank.
  3. Plan to use the filter as a permanent means of keeping the closed system free of entrained particles, checking the filter element periodically to see how much particulate is being captured. This should diminish over time. 

More Aggressive Cleaning Process.

  1. Add a polymer iron dispersive/cleaner such as our Eco-Green FerroKleen.
  2. Follow the guidelines for cleaning using FerroKleen.

Corrosion and corrosion deposits develop over time and they are difficult to remove in one cleaning process. It may take repeated cleanings to get most of the iron oxide and sludge out of the system.

Protecting the system from further corrosion:

Immediately after the system has been cleaned and flushed a corrosion inhibitor must be added to prevent corrosion from developing. Corrosion begins within minutes of being flushed out due to exposure to fresh oxygen in the water. Many contractors wait too long to chemically treat the system after flushing causing the system fluid to turn grey from iron oxide corrosion. While this is not detrimental to the system it will look dirty. Add corrosion inhibitors immediately to prevent this. We recommend the installation of a by-pass feeder on the closed loop to allow for chemical to be added to the system. Systems without a by-pass feeder almost never get proper chemical treatment and usually fail after just a few years. A properly treated system will last for the life of the building. 

Corrosion Inhibitors:

Typical corrosion inhibitors for closed loops will contain nitrite that acts as an oxygen scavenger. Once the nitrite has completely reacted with the oxygen in the system much of the nitrite will convert to nitrate as it absorbs oxygen molecules. This is the basis of corrosion protection for the majority of closed loops around the world. Nitrite also acts as a film protection for the surface of iron pipe, further protecting it from corrosion. 

Tolyltriazole compounds are another additive that is commonly used in conjunction with nitrite. This additive is often referred to as "Azole" or "Toly" among water treaters. Tolyltriazole is used as a filming type corrosion inhibitor for yellow metals like bronze, brass and copper. Many formulations include this with nitrite and is fed proportional to nitrite so you will just need to maintain your nitrite levels and the tolyltriazole will be dosed at the correct level. 

Molybdate is another common corrosion inhibitor that was used for decades. In recent years it has been phased out almost completely around the world as prices for molybdates rose to ridiculous levels. Molybdates are synergistic with nitrite which reduces the dosage required for both chemicals. 

Organophosphonates are now becoming the leading choice for closed loop corrosion inhibitors due to their low cost and excellent filming properties. They are not considered an oxygen scavenger so these inhibitors can be used in open systems that are exposed to oxygen without the fear of being depleted over time. Testing is done with an OP test kit. We recommend our CNTK0159-Z test kit. 

We can provide everything you need to properly clean, treat and test your closed loops. 

Typical savings of 40 to 70% can be expected when using our chemical formulations. 

Please contact us for a free consultation. We will evaluate your system and provide feedback on what is the best coarse to take. 

Richard S. Cannon

AWT Certified Water Technologist # 1253

Northern California Warehouse Solves Water Treatment Problem In Evaporative Coolers

Posted by Richard Cannon on

A Northern California warehouse was having problems preventing equipment failures and scale in nine industrial evaporative coolers and swamp coolers.They had limited maintenance staff and wanted a simple and safe way to control scale, corrosion and biological fouling. The evaporative coolers were located on the roof of several buildings making delivery of liquid chemicals difficult and hazardous. They did not [...]

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Battery Powered Level Sensor Makes Tank Level Monitoring Easy

Posted by Richard Cannon on

When it comes to monitoring the water level in small tanks most systems are very complicated, expensive and hard to install. The Aquatel line of Battery Powered Level Sensors seeks to solve all of these issues. Two systems are available from Aquatel. D110 System: Monitors up to six tanks simultaneouslyM107-BT will monitor one tank and wirelessly control a [...]

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Introducing the Stenner "S Series" pump

Posted by Richard Cannon on

Introducing ~ Stenner “S Series”                      This is no Small pumpNot all chemical metering pumps are created equally. This year Stenner really brought their A game with the introduction of the Stenner S Series microprocessor controlled peristaltic pump. I had my first glimpse of the new system [...]

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CAL-FIRE Remote Monitoring and Control System

Posted by Richard Cannon on

CAL-FIRE Remote Monitoring and Control SystemWhen the California Fire Department needed a way to remotely monitor and control water systems located at the Ben Lomond Conservation Camp in Santa Cruz CA. they called on Cannon Water Technology to engineer and build a system that was both reliable and cost efficient. The goal was to provide [...]

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Alarm Box With LED Flashing Strobe and Audible Alarm

Posted by Richard Cannon on

AL-MP2 Digital Alarm Box with Flashing Strobe and Audible AlarmIntroducing our digital input alarm and monitoring panel with microprocessor controller.This handy little box will let you know when something important is happening and needs to be dealt with.Our alarm and monitoring panel will sound a very loud audible alarm and display a very bright LED [...]

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Inca Gold Toilet Deodorizer Treatment

Posted by Richard Cannon on

Got a stinka? Try some Inca! Inca Gold Products makes porta potty chemicals that are environmentally friendly and safe to use in portable toilets. Trust Inca Gold porta potty chemicals and outdoor toilet supplies to keep your guests and customers happy.Whether you own or manage an RV park, marina, campground, or you sell RVs, you [...]

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