6 Steps to Protect an Industrial Boiler from Destructive Corrosion

You will need to carry out in-depth industrial steam boiler maintenance to protect your boiler from corrosion. 

Industrial boilers work under very tough conditions that can facilitate corrosion. Their high operating temperatures can greatly speed up corrosion. Thankfully, there are several steps that you can take to ensure that the corrosion slows down. You cannot completely stop corrosion but you can mitigate it to a large extent so that your boiler continues to function optimally for many years. 

Here are the industrial steam boiler maintenance procedures that you can carry out for reliable boiler performance and safety. 


1. Neutralizing Amines


You will have to neutralize amines if you want to prevent carbonic acid attack. But what is a carbonic acid attack? This is the primary route through which boiler corrosion occurs. 

Carbonic acid develops when carbon dioxide reacts with the condensate. Carbon dioxide may infiltrate the system due to thermal reactions of carbonates that naturally occur in makeup water. The condensate is very pure due to which even a small amount of carbon dioxide can lower the pH just enough to make it corrosive. 

You can spot a carbonic acid attack if you notice grooving in condensate piping. The pipe may become thinner towards the threaded fitting. You may also spot the same phenomena downstream of steam traps. 

Thus, it is necessary to arrest carbonic acid attacks by neutralizing them with special amine compounds. Neutralizing amines may include cyclohexylamine, morpholine and diethylaminoethanol. These compounds are volatile in nature and vaporize in the same way that carbon dioxide does in the presence of steam. When this happens, neutralizing amines then eliminate carbonic acid to bring the pH of water back to normal levels. 

Neutralizing amines have no effect on oxygen pitting which is another important factor behind boiler corrosion. 


2. Filming Amines


Filming amines work by developing a protective barrier that is impervious to oxygen and carbonic acid. When a filming amine is in use, the pH of the water must be maintained in the required range. The pH should be from 6.0 to 7.5. Neutralizing amines can help with this so they are included when filming amines are used. 

However, the protective layer that develops with filming amines is not completely perfect. It may be susceptible to damage. Hence, corrosion coupons are deployed to monitor the effectiveness of corrosion protection with filming amines. 

There are other possible issues with filming amines. They are not easy to apply. And in systems where filming amines have never been deployed, they can cause fouling. One way to avoid such a problem is to apply the filming amine gradually. 


3. Volatile Oxygen Scavengers


To protect against oxygen pitting, volatile oxygen scavengers may be used such as diethylhydroxylamine – DEHA. 

Oxygen pitting is another route through which boiler corrosion often transpires. Most people probably know that oxygen can be highly reactive and it can therefore cause corrosion if not fully removed. Oxygen dissolved in the condensate may corrode the boiler if it is not fully extracted from the feed water. Oxygen may also infiltrate the system due to the creation of a partial vacuum when steam cools and condenses. The resulting low pressure pulls in oxygen rich air from the surroundings into the system.

As the name suggests, oxygen pitting is visible in the form of small holes on surfaces. The problem of oxygen pitting may exacerbate if the pH falls too low. Oxygen pitting can lead to rapid failure in metal piping and components. Almost everyone knows how susceptible iron and carbon steel are to atmospheric oxygen. 

Hence, to protect against the adverse consequences of oxygen pitting, DEHA may be used. The primary advantage of DEHA is that it has fewer drawbacks as compared to filming amines. Another key advantage of DEHA is that it works in more than one way. First, it helps to scavenge oxygen which should be obvious from its name. Second, it makes metals less vulnerable to corrosion.   

One way to protect the boiler against carbonic acid attack and oxygen pitting is to use DEHA and neutralizing amines together. 


4. Pre-treatment


Pre-treatment equipment is a necessary part of boiler maintenance and corrosion protection since it helps to reduce the amount of dissolved carbon dioxide in the water which can later turn into carbonic acid. Hence, this equipment helps to limit the formation of carbonic acid in boiler systems. 

A water softener and dealkalizer unit can help water entering the boiler to reach the right pH level that will mitigate corrosion. 

It is also possible to use a reverse osmosis unit to reduce the levels of dissolved solids which can lead to corrosion. The reverse osmosis unit may also help to bring the pH level to the right range that will minimize corrosion. A feasibility study should be carried out to find out which system may be more effective and economical for boiler protection. 


5. Continuous Monitoring


Condensate monitoring is a key part of boiler protection and maintenance. It is influenced by the kind of treatment option that you have put into practice. Condensate may be monitored through the following methods.

  • pH level testing
  • condensate corrosion coupon usage
  • testing for both soluble and insoluble iron

one good idea is to carry out pH level testing for different points along the condensate return system to find out if any point has a pH level that may be detrimental for the system. 


6. Boiler Room Training


Boiler room training and boiler training seminars are your answer to high quality boiler maintenance and protection. You can gain knowledge about the best practices that will mitigate corrosion in your boiler. You can put this knowledge into practice so that your boiler can provide reliable service for many years to come. 

This knowledge will also empower you to carry out in-house maintenance so that you can keep your boilers running with minimal risk of a disruptive breakdown.

6 Steps to Protect an Industrial Boiler from Destructive Corrosion