Corrosion issues in power plants prolongs maintenance, increases operating costs, reduces efficiencies and poses safety risks to workers. To optimize power-generating equipment, corrosion prevention is vital. This means ensuring the successful installation of insulation and protective coatings on items that are susceptible to corrosion.
Types of Corrosion in a Power Plant
- Oxide corrosion: An electrochemical process on metal surfaces when oxygen molecules dissolve in water. This type of corrosion occurs when lagging isn’t installed properly, or when protective surface coatings fail or were never applied.
- Galvanic corrosion: A process that occurs when two dissimilar metals contact each other, creating an electrical reaction that promotes corrosion.
- Hot corrosion: Accelerated corrosion due to the presence of salt contaminants that form molten deposits, which damage protective surface oxides.
- Erosion: The combination of high fluid surface velocities and an aggressive chemical environment that wears away a surface’s protective scale or coating.
Power Plant Corrosion Danger Zones
- Hot and cold piping systems
- Boiler tubes
- Welding seams
- Flue inlet gas ducts
- Bypass ducts
- Scrubber outlet ducts and modules
- Areas containing demineralized water
- Stack liners
- Fuel handling areas
- Collection sumps
The Consequences of Foregoing Corrosion Prevention in a Power Plant
- Safety risks: When corrosion affects systems carrying steam or hot water—such as pipes—material or welds may fail, causing bodily injury or death.
- Fouling: Power plant systems foul because of the ingress of moisture, dust or salt in the air.
- Pipe corrosion: Insulating with an outer finish or jacketing keeps water from contacting tank shells or pipes, preventing corrosion, pitting, cracking and failure.
- Contract-related fines: When corrosion affects a plant’s system, it may not start up after a maintenance outage, leading non-delivery fees for being out of service.
- Pollution control: Corrosion in tanks may hinder a plant’s attempts to control sulfur emissions in the environment. Sulfur emissions lead to acid rain, which damages buildings and other structures in a power plant.
- Boiler tube problems: Water, steel and dissolved oxygen within boiler units causes boiler tubes to oxidize and corrode. The corrosion forms grooves within the tubes that lead to cracks and boiler failures.
- High maintenance costs: Corrosion can account for up to 75 percent of a plant’s arrest time during maintenance and up to 54 percent of production costs.
- Gas or air leaks: Unaddressed plate corrosion leads to air or gas leaks. The problem generally occurs when the lagging system fails.
- Flue gas inlet duct problems: Gases within ducts attack the system physically and chemically.
- Scrubber outlet duct moisture: Outlet ducts generally have a lower temperature than inlet ducts, making them more susceptible to condensation.
- Flue liner failures: Freestanding stacks without windshields or protective liners suffer thermal shock and chemical attacks.
- Low-temperature hot-corrosion in gas turbines: Transient metal oxides react with sodium sulfate, forming eutectic salts that prevent the formation of protective alumina or chromia.
Corrosion in power plants leads to costly repairs, prolonged maintenance, material losses, poor performance and, if left untreated, failure. Industry experts recommend corrosion prevention in the form of preventive and control strategies, such as regular inspections and the use of protective coatings. The success of these coatings, however, depends on creating the optimal conditions to clean the respective surface and allow the coatings to dry according to the manufacturer’s instructions.
Polygon offers temporary climate and humidity control solutions that create the ideal environment for surface preparations and coating. The custom-built technologies accommodate areas of any size so the space has the perfect temperature and relative humidity levels, regardless of the weather outside. Call today to learn more about how Polygon assists with corrosion prevention.
[Photo from Libelul via CC License 2.0]