Corrosion refers to a process of change in the structure of metals, which affects both its chemical and physical composition. It leads to the loss of aesthetic appeal and structural strength. Even though stainless steel is fabricated to stand to corrosion, some situations can push the metal to its limit and lead to corrosion. For instance, stainless steel boat railings immersed in salty seawater are in a constant corrosive environment. The same thing applies to the hull and propellers that stay immersed for very long periods. Here is a look at some ways through which stainless steel parts and boat fittings can undergo corrosion in seawater:
Stainless steel can be affected by galvanic corrosion. It occurs because of electrical exchange between two or more metals that have varying degrees of chemical reactivity. All metals, including stainless steel, have atoms that contain freely moving electrons. Whenever there is contact between the metals, the electrons move freely from the least reactive metal to the most reactive one. For instance, a galvanic reaction when the stainless steel propeller on your boat is exposed to an aluminium surface. Stainless steel, being the more reactive of the two metals, receives electrons from the aluminium surface. This leads to the formation of an alkaline hydroxide solution that damages the steel and other parts made of materials such as wood.
It is important to check your boat for steel parts affected by galvanic reactions so that they can be repaired or replaced immediately. Paint blistering on the edges of the steel part is an early symptom of galvanic reactions.
Stray Current Corrosion
Stray current refers to electrical charges that flow through the ground and seawater. It results from natural causes such as lightning or dumping excess electricity into the ground using cables. Stray current moves through stainless steel because the metal structure has charged ions. The movement of the stray currents from one point to another corrodes the point where the current is departing from. You can reinforce the resistance of your stainless steel parts using epoxy coated pilings to reduce possible damage.
Stainless steel can only be free from corrosion if it is exposed to oxygen. It needs oxygen to form a protective layer of chrome oxide that prevents rust. Crevice corrosion results from the accumulation of sand, fibrous gaskets or tightly fishing nets strapped tightly to stainless steel. This traps the moisture between the stainless steel and the destructive deposits. By doing so, a barrier occurs on the surface of the stainless steel and cuts out the oxygen supply, compromising the formation of the protective chrome oxide. This leads to rusting. Keep stainless steel surfaces on your boat free from deposits through regular cleaning.
For more information or advice, contact a custom stainless steel fabrication business.