To solve corrosion in boilers, you must first determine the type of the system. Boilers are either steam-producers or hot water recirculators. Then appropriate chemical solution can be applied to address the problem.
Corrosion in Hot Water Recirculating Boilers
For hot water boilers, corrosion is typically distributed and spread across the system. Most, if not all metal tubes, are rusted. The reason is that the rate of mild steel corrosion greatly increases in low to mid pH range at elevated temperatures. Nitrite is the most suitable chemical to control corrosion in this type of boiler. Nitrite will passivate either mild or inexpensive version of stainless steel. Typically, nitrite is blended with silicates and tolytriazoles (TT) and is boosted with a pH buffer. Silicates and TT provide protection on aluminum and copper.
Innovation in technology now offers P indicator in chemical solutions. P indicator calculates the hydroxide alkalinity of water. Add it to the system and when water turns into a pink lemonade color, you have enough of the chemical. This eliminates the need to perform other tedious chemical testing. Just verify the color every other week and you know you have a good corrosion protection. Our anti-corrosion chemical for recirculating boilers is Boiler Chemical 2388D.
Corrosion in Steam Boilers
Corrosion in steam boilers is more complicated. You have two types: either dispersed on all tubes, or localized as small corrosion pits.
For dispersed corrosion, water pH should be boosted. At low pH ranges, mild steel is exponentially more corrosive. Water pH should be maintained above 10.5 to minimize the rate of metal breakdown and to keep polymers in good working condition -- preventing any hardness in the solution. Typically, sodium hydroxide or potassium hydroxide is used to boost boiler water pH. Our alkalinity product is Boiler Chemical 2425.
If there are corrosion pits, there is not enough sulfite in the feedwater tank. Sulfite is used to remove the water’s dissolved oxygen (which will make mild steel vulnerable for corrosion at elevated temperature). You should maintain a minimum residual of sulfite to ensure you have no dissolved oxygen and provide additional protection against oxygen spikes entering the system. Our sulfite-based product available is OS1537LF.
