In the marine environment there are five zones or conditions; Marine atmosphere, subjected to splash, tidal environments, full immersion and mud. Although one might think that all marine environments are equally corrosive this is not the case, each of these unique primary conditions subject marine fasteners in Minneapolis to different degrees of corrosiveness, all depending on the material in question.
It is not just these five corrosion zones that have an effect on fastener corrosion resistance; the velocity of the sea water, the degree of pollution, the temperature as well as the hydrogen evolution from the electro-chemical reactions found in the typical marine environment.
The first documented failure of fasteners used in a marine environment goes back to the mid 1700s when iron nails that were used to fix copper sheeting to the hull of HMS Alarm corroded to the point where there was loss of the sheeting. This is not only the first documented example; it is a classic example of galvanic action in seawater. Galvanic corrosion is by far the most important form of corrosion that must be considered when marine fasteners in Minneapolis are being selected.
By its nature a fasteners system is usually made up from a minimum of two dissimilar metals; one of the metals acts as the anode, which means it corrodes and the other metal is the cathode which does not corrode.
When selecting fasteners for use in the marine industry the galvanic effects of the materials are of primary importance. The fastener must be the cathode which means the metal must be nobler than the metal used as the anode. A typical example of this situation is a stainless steel fastener and an aluminum base metal structure. Although this is a good example of the use of noble metals it is actually a poor example as the corrosive effects of seawater will cause a galvanic action which will eventually eat away at the hole, enlarging it to the point where the stainless steel marine fasteners in Minneapolis will simply fall out. This example should not be used in reality unless grease which is specially compounded for this specific application is used.
The marine engineer is well acquainted with the different materials that are used in the manufacture of marine fasteners that are to be employed in one of the five primary corrosion zones with the emphasis being on corrosion resistance, strength, longevity and safety.