Boil Out & Cleaners

New boilers are not clean. Manufacturing and installation leave mill scale, oils, and construction debris on internal metal surfaces. Operating boilers accumulate hardness scale, iron oxide deposits, and sludge over time. These contaminants reduce heat transfer efficiency, create conditions for under-deposit corrosion, and limit the effectiveness of ongoing water treatment chemistry. Establishing a clean baseline, at commissioning and periodically throughout the boiler’s service life, is a foundational step in any water treatment program.

Alkaline boil-out is the standard procedure for new boiler commissioning and general deposit removal. A solution of caustic soda, soda ash, or a formulated alkaline cleaner is circulated through the boiler at low fire for 12 to 48 hours. The chemistry saponifies oils and greases, disperses soft deposits, and passivates steel surfaces through formation of a protective magnetite layer.

When hard mineral scale, calcium carbonate, calcium phosphate, or iron oxide deposits, has accumulated to the point that alkaline treatment cannot remove it, inhibited acid cleaning is required. Inhibited hydrochloric acid dissolves mineral scale while corrosion inhibitors protect the base metal, but the procedure is more complex, generates hydrogen gas, and requires appropriate neutralization and disposal of spent solution.

Acid cleaning is always followed by a passivation step to protect freshly cleaned metal surfaces from flash corrosion, either a chemical passivation solution or immediate startup with active water treatment chemistry. Key indicators that a boiler is a candidate for cleaning include rising fuel consumption relative to output, elevated tube temperatures, reduced steam capacity, and deposit weights from tube inspections above roughly 15 to 20 grams per square foot of heat transfer surface. All cleaning work should be documented, including chemistry used, operating conditions, rinse water quality, and observations of deposit character and quantity.

Read the full technical guide in our Knowledge Center