Technical definition
Dissolved Copper is a measurement of the concentration of copper present in the heating system water in dissolved ionic or soluble chemical forms, expressed in milligrams per litre (mg/L).
Within a heating system, dissolved copper is commonly associated with the corrosion or chemical attack of copper-containing components, including copper pipework, heat exchangers, fittings and copper alloys such as brass. Fernox uses dissolved-metal testing as an indicator of the extent of corrosion occurring within heating systems. (Fernox)
Dissolved Copper can therefore provide an indication of active or recent corrosion of copper-containing materials, particularly when considered alongside pH, chloride, conductivity, inhibitor concentration and other dissolved-metal results.
Simplified definition
Dissolved Copper measures how much copper has dissolved into the heating system water.
Because many heating systems contain copper pipework, heat exchangers or fittings, elevated levels can indicate that copper-containing components are being corroded or chemically attacked. This can provide an early warning before more obvious system damage occurs.
Dissolved Copper is important because elevated levels can provide evidence that copper-containing materials within the system are deteriorating.
An abnormal or elevated Dissolved Copper result may indicate:
Active corrosion of copper pipework or components.
Unsuitable system-water pH.
Insufficient or ineffective corrosion-inhibitor protection.
Elevated chloride or other aggressive dissolved salts.
Residual soldering flux or installation chemicals remaining within the system.
Contamination from cleaning chemicals or other substances.
Oxygen entering the system through leaks or repeated topping-up.
Changes in water chemistry following draining, flushing, refilling or maintenance.
Residual soldering flux is particularly relevant in copper systems. Fernox advises that systems should be flushed after soldering to minimise the likelihood of corrosion problems caused by flux residues.
Continued copper corrosion can contribute to:
Deterioration of copper pipework and heat exchangers.
Pinhole leaks in susceptible copper components.
Release of copper corrosion products into the circulating water.
Deposits or staining within the system.
Interaction with other metals within mixed-metal systems.
Fouling of heat exchangers or narrow waterways.
Reduced component life.
Leakage or premature component failure where corrosion becomes severe.
Dissolved Copper is especially useful because corrosion may be taking place before large quantities of visible corrosion debris have accumulated. A rising dissolved copper concentration can therefore help identify a developing water-quality problem at an earlier stage.
It should be considered alongside parameters such as pH, Chloride, Conductivity, Iron, Aluminium, inhibitor concentration and Suspended Solids when assessing the overall corrosion condition of the heating system. Fernox includes copper among the chemical parameters used within its laboratory water-testing services.
Dissolved Copper should not normally be assessed in isolation. The presence of copper in the water does not automatically mean that serious corrosion is occurring, as small concentrations may originate from the filling water or other sources.
It is particularly important to distinguish between Dissolved Copper and total Copper:
Dissolved Copper represents copper that is chemically dissolved in the water and can be particularly useful as an indicator of active or recent metal dissolution.
Particulate Copper consists of insoluble copper-containing corrosion products or debris suspended in the water.
Total Copper, where measured, may include both dissolved and particulate forms.
This distinction can provide useful diagnostic information. Elevated Dissolved Copper may suggest that copper is currently being released into the circulating water, whereas elevated total Copper with relatively low Dissolved Copper may indicate the presence of existing corrosion products or debris.
The result should therefore be interpreted alongside the system materials, filling-water chemistry, pH, chloride concentration, treatment regime, previous test results and inhibitor level before determining whether corrective action is required.
