This is terrible damage caused by the Sikkens varnish.
It simply trapped moisture along the screws caused the beautiful
(and expensive) cedar deck to completely rot around all
The material in the screws can also be a contributing factor
to the wood decay. We recommend stainless steel screws for
any exterior application. Linseed oil, varnish and Linseed Oil Paint products have excellent rust inhibitors and would
have prevented this problem too. In Europe, the linseed
oil and paint is now used as undercoating on cars.