How to Fight Boiler Corrosion

If you’re in charge of your boiler maintenance, you know the struggles of dealing with things like feedwater, but corrosion is a special concern. Corrosion is created when parts of the system are exposed to water and oxygen which can result in disintegrating parts and malfunctioning equipment. If left untreated, corrosion causes leaks and ultimately failure. With the right preventative maintenance, this doesn’t have to be the case!

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So, what can you do to combat this huge issue? If you look for corrosion and understand what causes it, then some preventative maintenance can work to extend the life of your boiler and keep operations running smoothly. Read on to get all the information you need!

The Cause

No matter the type of boiler you work with, corrosion is always a risk and not everyone understands the preventative maintenance required to keep prevent equipment damage. As mentioned before, corrosion is commonly caused by oxygen or improper pH control. This can create holes in economizers, boiler tubes or feedwater piping resulting in boiler leaks and a pricy fix (see the next section for more). There are many forms of corrosion and they are not treated equally.

Check out these different types and what they mean:

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  • Caustic Corrosion. When a concentrated caustic substance dissolves the protective magnetite layer of a boiler. This is commonly caused by boiler water pH is too high, steam blanketing (poor circulation) or local ‘film boiling’. If your boiler has a porous scale, then under deposit corrosion is also possible. Boiler water pH should be a part of your logbook.
  • Acidic Corrosion. Results from the mishandling of chemicals during acid cleaning operations or the boiler pH being run too low to passivate the carbon steel surfaces of the boiler. Boiler water pH should be a part of your logbook.
  • Pitting Corrosion. This is one of the most destructive types of corrosion, as it can be hard to predict before a leak forms. Pitting is a localized form of corrosion, in which either a local anodic point or more commonly a cathodic point, forms a small corrosion cell within the surrounding normal surface. Oxygen in feedwater is a common cause of boiler tube pitting. If your boiler is pitting, investigate the proper operation of your deaerator or feedwater tank and chemical treatment. If you have a hot water system, oxygen pitting can occur if the system has a leak and is bringing in freshwater.caustic corrosion boiler maintenance
  • Crevice Corrosion. This type of corrosion is also a localized form of corrosion and usually results from a crack in the boiler that does not get good circulation to rinse away caustic.
  • Galvanic Corrosion. Galvanic corrosion is the degradation of one metal near a joint or juncture that occurs when two electrochemically dissimilar metals are in electrical contact in an electrolytic environment. So, dissimilar metals may need a special dielectric joint, sacrificial anode, or active cathodic protection system to prevent this phenomenon.

The Cost

Because of a boiler’s vital function for any facility, their breakdown can result in safety concerns, not to mention a huge cost in order to replace or repair the system. Repair costs to boilers can be steep and can range anywhere from a few thousand dollars to over $1 million depending on size, function, and accessibility. But it doesn’t stop there. This price is in addition to the expense of operational downtimes to get the boilers repaired or replaced and up and running properly.

What You Can Do

Even the most aggressive forms of prevention can’t stop minor corrosion from eventually happening. But, with the right approach, the effects of corrosion can be minimized and extend the life of your boiler.

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Here’s what to do to minimize the effect of corrosion before it happens:

  • boiler repair and replacementUse a boiler logbook. Regularly tracking the normal operation of your boiler room equipment makes it easy to spot when something critical changes. Deaerator pressure or feed-tank temperature changes will give advance warning of a more expensive corrosion problem. pH changes could indicate problems with water treatment or process contamination.
  • Treat Feedwater. Additives can ensure that any oxygen that makes its way to the boiler in the feedwater is rapidly absorbed before it has the opportunity to form corrosive cells and blisters. Work with a good water chemistry company to stay on top of your boiler water.
  • Implement a strict, regular service program to ensure the boiler stays clean and free of scale and corrosion problems. If the boiler is being inspected, the root cause can be addressed early, avoiding more costly repairs.
  • For hydronic systems, check for leaks and monitor the quantity of make-up water. Hot water heating systems shouldn’t need make-up water unless something is wrong. Call your service provider to fix the leak right away, or you may be replacing the boiler next year.

Here’s what to use after corrosion has already reared its ugly head:

  • Oxygen Scavengers to prevent pitting
  • Scale inhibitors to prevent deposits
  • Alkalinity to control pH
  • Condensate line protection to control condensate pH
  • Train your crew on boiler preventative maintenance and water chemistry tests
  • Document and report any signs of corrosion to your boiler service provider and your water chemical company so they can help prevent further damage.

Use our tips to ensure the longevity of your boiler. Need some expert advice or repair services? Contact Rasmussen Mechanical today to schedule your free consultation.

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