Technical Data: Corrosion
Corrosion is an important factor when selecting an anchor. There are two types of corrosion - atmospheric and electronic.
Atmospheric corrosion is caused by the action of air on the metal, electrolytic corrosion may occur when different metals are in contact with each other. This creates an electrolytic couple which causes the gradual destruction of one of the elements.
The table below shows various combinations of metals normally found in sea water atmosphere: vertical axis (metal of pad to be fixed).
horizontal axis (metal of fixing),
This effect is further accentuated if the difference between the two surfaces is bigger.
- The attached metal is not subjected to galvanic corrosion and benefits, in fact, from an effect of galvanic protection (low if the difference in potential is small, higher as the difference in potential increases).
- The galvanic effect is influenced by the size of the surface area of the two metals:
- if the base material surface area is smaller, corrosion is accelerated,
- if the base metal surface area is bigger, corrosion is slower.
Furthermore SPIT is carrying out ongoing corrosion trials in a marine atmosphere. Each year, anchors are examined and analysed. These trials provide a basis for accurate feedback to our customers for future product development.
All our metal anchors are zinc coated and passivated. Where anchors are intended for use in aggressive atmospheres (near coasts, chemical plants, etc.) we recommend the use of hot dip galvanised or stainless steel.