Definition - What does Harmful Chlorides mean?
Harmful chlorides refer to those chlorides that are harmful to the environment and cause corrosion to the materials. Some harmful chlorides are:
- Calcium chloride
- Magnesium chloride
- Sodium chloride
- Potassium chloride
- Ammonium chloride
The presence of chlorides enhances the corrosion of materials. It aggravates corrosion conditions in stress corrosion and pitting corrosion of materials and concrete.
Corrosionpedia explains Harmful Chlorides
Harmful chlorides are the cause of corrosion. Some are more corrosive than others. For example, both calcium and magnesium chlorides are less corrosive than sodium chloride, but they are more expensive than conventional salt. In a study, it was found that aqueous solutions of the inhibited liquid calcium chloride cause less than 80% to 90% of corrosion compared to sodium chloride.
On the other hand, both magnesium chloride and sodium chloride are very corrosive to the metal surfaces of automobiles. The rate of corrosion depends on the type of metals that come into contact with these chlorides. Since automobiles are made of steel or various alloys and aluminum, magnesium or a combination, the corrosive effects are varied and one needs to consider proper coatings.
Chloride causes the cracking of stainless steel. Austenitic stainless steels produce stress-corrosion cracking in chloride-containing hot solutions. The zone of high chloride concentration suffers from pitting or crevice corrosion. It may also create problems in tap water. Steel in concrete corrodes when chloride at cracks and joints exists.
Steel corrosion in concrete is the result of intrusion of harmful chloride ions into reinforced concrete and the presence of oxygen and moisture to sustain the reaction. A chloride-containing admixture also causes corrosion.