Whenever fitting or changing a sacrificial anode the most important THING we should consider is to replace the serrated fan disc washers under the nuts and replace the anode backing sheet on wood and GRP hulls. In this case, Unprotected fixing studs, nuts and washers should be well greased or paint coated after assembly. Furthermore, Zinc and Aluminium Hull Anodes are best fit for use in salt and brackish / estuarine waters. Moreover, magnesium hull anodes are best fit for use in fresh waters. Zinc hull anodes are best fit for use in salt waters.