The term "galvanization" encompasses a few different methods intended to achieve the same result - a screw more resistant to corrosive environments, which lasts longer than those made with traditional steel. Electro-plating is one method by which a layer of zinc is applied to a screw. Another is called hot-dipping, which is a process that results in the thickest layer of zinc. The treated wood industry suggests to only use galvanized or stainless steel screws in conjunction with any project utilizing lumber that has been chemically altered to extend its shelf life.
Between the heat, humidity, and devastating effects of wind-borne salt, coastal environments have long played havoc with construction. Galvanized screws are recommended for use in almost any project near the ocean. Salt, in particular, quickly wears away plain steel screws, turning them rusty in a short period of time and necessitating repairs more often. Galvanized screws included as fasteners in either wood or metal projects will almost certainly last longer.
Treated wood, which is prized for its resistance to fungal decay and insect attacks, is created by forcing chemical preservatives into boards through a vacuum and pressure process. The problem is that the same preservatives that extend the life of lumber, attack and destroy the integrity of traditional steel screws. This scenario is where galvanized screws become the fastener of choice. The zinc coating on these screws allows them to resist the rust and deterioration found in other types of fasteners.
Though a coastal environment is especially brutal, galvanized screws can be used in a variety of outdoor projects anywhere weather is occasionally harsh. Installing fencing using treated wooden posts, house or barn roofs, and outdoor furniture are just a few examples. Materials exposed to rain, sun, snow, or intensely cold temperatures could benefit from the use of galvanized screws as fasteners.
There are few situations where galvanized screws could be a detriment. The primary factor to consider is cost, since the process of coating screws with zinc creates an additional expense, which might not be necessary if the project is indoors and not subject to environmental or chemical corrosion. There is usually no need for these specialized screws with interior remodeling or construction projects. Regular, old-fashioned steel screws work fine in locations protected from inclement weather or other stresses.