Flux Induced Pitting

What is Flux Induced Pitting?

Flux Induced Pitting is caused by excess flux entering the inside of a pipe, preventing the formation of the protective corrosive layer inducing pitting and later leaks.

How Does Flux Cause Leaks?

Copper develops and relies on a protective layer of copper oxide and copper carbonates formed by reacting with the water it carries. Problems can occur however if that layer fails to form. Issues with water quality can arise but also issues with corrosion.

Flux is used to create an oxide free layer during jointing to ensure the solder forms a secure joint. To that effect, if there is any residual flux on the inside of the pipe or fitting after the joint has been made the protective oxide layer cannot form during operation.

Without the oxide layer pitting will occur. Similar to Erosion Corrosion turbulence will form around the pitting exacerbating the corrosion, resulting in pinhole leaks. Leaks induced by flux typically develop after one to five years after commissioning.

How Can You Avoid Flux Induced Pitting?

Overall, Flux Induced Pitting is a direct result of applying too much flux to the joint. Ensure you using flux sparingly, and only apply it to areas where the pipe and fitting will overlap.

Some fluxes are more aggressive than others, and furthermore water soluble fluxes are also available. Flushing systems with hot water prior to commissioning will also help remove residual flux.

Finally you can read our instructions for connecting Flowflex End Feed and connecting Flowflex Solder Ring carefully for further advice.