Corrosion Promotion Conditions

The most common conditions, some of which are inherent, while others are caused by poor design and /or installation include:

  1. Naturally occurring impurities in the supply water such as chlorides, sulphates and peat acids. ‘Soft waters’ also, are generally more corrosive than ‘hard water’.
  2. Chemical impurities introduced into systems such as corrosive residues of soldering flux and sodium chloride from water softeners.
  3. The presence of dissimilar metals and other conditions which create a ‘potential difference’ leading to electrolytic corrosion, with water acting as the electrolyte, e.g.
  4. Steel, cast iron, copper, brass and aluminimum present in a variety of combinations
  5. Copper swarf settling onto steel forming short-circuited electrolytic cells.
  6. Copper plating out onto steel from flux residues or in areas of cupro-solvent mains water supplies.
  7. Anodic/cathodic crystals or areas on the internal surface of steel components.
  8. Carbon deposits formed as a result of welding oily or greasy steel.
  9. oxygenated water, due to system faults (such as micro-air leaks at screwed/compression joints or pumping over) or as the result of oxygen diffusing through any plastic pipework, leading to oxide corrosion.
  10. Sediments or substances of any kind in contact with steel, leading to crevice corrosion.
  11. Stressed steel, as for example in pressed steel radiators.
  12. The presence of organic matter, particularly anaerobic sulphate reducing bacteria.
  13. Stray electric currents, caused by an earth leakage fault on site.
Electrolytic corrosion increased drastically with temperature and with aeration. Oxide corrosion increased, despite depleting oxygen levels, up to about 78°c