Rusting is an important phenomenon accompanied with the corrosion of carbon steel and the formation of corrosion products such as iron oxides is an a biotic process of chemical reactions.

Technical Overview: Oxygen Corrosion in Closed Loops

In a perfectly sealed closed-loop chiller system, dissolved oxygen is quickly consumed by initial, minor surface reactions, rendering the water inert and stable. However, when fresh oxygen is continuously introduced, it triggers severe electrochemical corrosion.

1. The Chemical Process
Oxygen corrosion is an electrochemical reaction where dissolved oxygen acts as a powerful electron acceptor, accelerating the oxidation of system metals (typically carbon steel, copper, or iron).

   •Anodic Reaction (Oxidation of Iron)
   •Cathodic Reaction (Reduction of Oxygen)
   •Resulting Precipitate (Rust)

2. Root Causes of Oxygen Ingress
Closed loops are rarely perfectly closed. Oxygen enters via:

   •Fresh water makeup: Frequent refilling due to undetected leaks brings in highly oxygenated city water.
   •Defective expansion tanks: Failed bladders or open-style expansion tanks allow air-water contact.
   •Suction-side leaks: Seals and packing on the suction side of pumps can draw air into the system if pressure drops below atmospheric levels.
   •Permeation: Non-barrier plastic piping or degraded rubber hoses.

3. Operational Consequences
   •Pitting Corrosion: Unlike uniform corrosion, oxygen causes localized "pitting." This concentrates the metal loss on a tiny area, rapidly punching holes
     through pipe walls and heat exchanger tubes.
    •Fouling and Sludge: Precipitated iron oxides travel through the system, creating a thick, black or reddish sludge.
    •Efficiency Loss: Sludge settles in low-flow areas and coats chiller barrels. Iron oxide is an excellent insulator;
     a thin layer drastically reduces heat transfer efficiency, skyrocketing energy bills.
    •Component Failure: Abrasive rust particles erode pump impellers, clog control valves, and foul strainers.

Stop the Silent Chiller Killer: Protect Your Bottom Line from Oxygen Corrosion with ScaleAway Preventative Maintenance Program

Closed Loop Dosing with ScaleAwayA900
ScaleAway A900 for Steel and Copper coils
ScaleAway A908 for Aluminium coils
ScaleAway A171 Biocide and Algaecide for Cooling Water systems

Contact us TODAY to take advantage of our scheduled preventative maintenance services!

Alternatively, speak to one of our service technicians about acquiring ScaleAway Industrial Water Treatment Products for your maintenance team to do your own chiller cleaning and management in-house!

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