Can Galvanised Steel be used with Stainless Steel?
Reactive Corrosion or deterioration of the galvanising can occur when galvanised steel comes into prolonged contact with stainless steel in salt water or salty, damp air.
The degree of galvanic reaction depends on the wetted area ratio, e.g. a stainless steel shackle or anchor connector will probably react with the last link of an anchor chain but is not likely to have any noticeable effect on a galvanised anchor.
Stainless steel is a nobler metal (Cathodic) than Galvanised steel (Anodic)
Galvanic corrosion will occur in the less noble metal
Generally speaking, this is a slow process which can be monitored and dealt with before it develops into an unsightly or severe issue, e.g. galvanised shackles are easily replaced, the last link of a chain can be removed with bolt croppers, angle grinder or hacksaw.
Coating the last part of the the galvanised components will also help to prevent or slow down the corrosion e.g. the last half metre of your anchor chain or the end of the anchor shank near the stainless connection. An epoxy coat is best, but any application that insulates the stainless from the galvanised should do the trick.
The images show what can happen with acute galvanic reaction, but the length of time it has taken for the deterioration to occur needs to be taken into account to judge the speed or severity of the corrosive deterioration.
In this photo illustration, the owner advised that the chain was over 15 years old and the Delta Anchor and large galvanised anchor shackle were approximately six years old.
The stainless steel shackles were also fitted around this time.
Just so you know – the owner cut off the offending links without delay which solved the problem.
Although unsightly, there is still plenty of metal left to take the load, but the problem would have spread further down the chain if it hadn't been dealt with.
It is important to note that the corrosive process may accelerate when the galvanising is not pristine.
N.B. Saltwater content varies quite widely according to geographical location.
Some areas may be particularly saline or chemically aggressive towards any metal surface.
Read more about the more technical aspects:
BRITISH STAINLESS STEEL ASSOCIATION
Image 1 illustrates what can happen to a single link of galvanised chain when used with a stainless steel shackle - note that the galvanic corrosion has only acted in one direction.
Image 2 illustrates what can happen to the end links of a galvanised chain rode when used with a stainless steel shackle - note that the galvanic corrosion has only acted on the chain and not on the larger galvanised shackle and, significantly, not on the anchor.
