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 is dependent on the ratio of wetted area 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 serious issue e.g. galvanised shackles are easily replaced and the last link of a chain can be removed with bolt croppers, angle grinder or hacksaw.
The images show what can happen but don't help without any insight into the length of time it has taken for the deterioration to occur.

In this instance, the owner advised that the chain was over 15 years old and the Delta Anchor and large galvanised anchor shackle approximately 6 years old.
The stainless steel shackles were also fitted around this time.
The owner was advised to cut off the offending links without delay.
Although unsightly there is still plenty of metal left to take the load but the problem will spread further down the chain if it isn't dealt with.

It is possible that the corrosive process is accelerated when the chain is not in pristine condition.

N.B. Salt water content varies quite widely according to geographical location. Some areas may be particularly saline or even chemically aggressive towards any metal surface.

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.

Galvanic Corrosion 2

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 importantly not on the anchor.

Galvanic Corrosion