Anti Corrosive Coatings in Waste Water Treatment Facilities

January 1, 2010

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Wastewater treatment facilities often require the highest-performing anti-corrosive coatings, particularly in wastewater tanks and containers, because of the severely corrosive nature of many elements and chemicals used in treating wastewater. It often takes a special kind of anti corrosive coatings to combat these harsh corrosive elements and maintain tank longevity. 

What are the most common sources of corrosion in wastewater tanks?  Here are a few: 

1. Chemical and biological elements
In sewage treatment procedures, chemical and biological elements are introduced inside the storage tank and allowed to react with each other. This subjects the tank’s concrete material to attacks from acidic by-products. Sulfate attacks, in particular, cause the concrete to expand, while carbonation causes shrinkage, contributing to overall concrete degradation. 

2. Extreme change in temperatures
In treatment facilities often exposed to extreme and alternating hot and cold conditions, concrete surfaces may degrade due to the continual exposure to the freezing and thawing process. 

3. Abrasive elements
Flowing sewage water may contain rocks, sand or solid materials that strike the inner concrete surface of the tank, causing wear and tear through time. The failure of anti corrosive coatings to protect the tank from this abrasive damage hastens surface degradation. 

Repairing Corrosion in Sewage Tanks

When anti corrosive coatings within the storage tanks fail, facility managers must follow the following remediation guidelines below:

1. Assess the structural condition accurately
A thorough inspection of the structure is needed to identify whether or not progressive corrosion is indeed taking place, taking into account the tank’s history. A visual inspection of the tank’s condition is also important, and this should include the condition of the anti corrosive coatings previously applied.

2. Determine the extent of corrosion
Skilled anti corrosive coatings contractors can conduct detailed data gathering to determine the severity of corrosion. A surface sampling may be conducted, as well as some tests to determine which areas of the tank suffer from coatings failure. Knowing the extent of coatings failure and the severity of corrosion will provide a sound analysis and a priority plan to repair the corrosion problem. 

3. Come up with an action plan for repair
The repair plan should include freeing the surface from contaminants through blast cleaning, to increase surface profile and porosity. In cases of voids and air pockets, filler materials should be injected into the surface to create a smooth surface. The substrate barrier may include fast-setting cement-based materials and elastomeric urethane based linings. The anti corrosive coatings system should be applied following manufacturer’s data sheet, and should be chosen for its high resistance to toxic chemicals and ease of application, due to the peculiar demand of wastewater tanks. 

4. Setup a continuous and sustainable corrosion monitoring and remediation plan
Corrosion is always an ever-present menace particularly in wastewater treatment plants. it is important that a regular monitoring and remediation plan should be established in the facility to avoid costly repairs. Periodic inspections can improve early detection and timely remediation of corrosion. An SOP on tank repairs and maintenance, one designed for easy implementation, should also be put up, and should involve detailed surface preparation, coating application, post-curing procedures, and the like.

Wastewater treatment tanks may pose great challenges in corrosion repairs, but early diagnosis, a clear identification of the problem, and an accurate intervention plan can go a long way in preventing corrosion from recurring at high costs.

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