Our brown water gets discharged from the head overboard via a hose, ball valve, an elbow, and finally a thru-hull fitting. Our 2004 boat part manual states that these 4 elbows are brass. After 9 years, this is the state of our bronze thru-hull fitting in contact with the brass in salt water:
A straight connection without the brass elbow: ball valve screwed onto a thru-hull fitting - all bronze:
Brass is an alloy of copper and zinc. If bronze and brass are interconnected and are then immersed in salt water (an electrolyte), a galvanic cell is created that results in the dissolution of the zinc (dezinfincation), leaving a soft, porous, weaker structure. It deceptively retains its shape but is actually devoid of its original soundness. It was very easy to break our corroded fitting. Not so easy with the straight fitting.
Bronze is a noble metal with a range of potential for galvanic corrosion much more acceptable than brass.
A lot of those fittings are also available in marelon which is compound made of reinforced polymer and additives. Unfortunately their product does not fit in our case size wise. Too bad. Seems the way of the future.
A straight connection without the brass elbow: ball valve screwed onto a thru-hull fitting - all bronze:
Brass is an alloy of copper and zinc. If bronze and brass are interconnected and are then immersed in salt water (an electrolyte), a galvanic cell is created that results in the dissolution of the zinc (dezinfincation), leaving a soft, porous, weaker structure. It deceptively retains its shape but is actually devoid of its original soundness. It was very easy to break our corroded fitting. Not so easy with the straight fitting.
Bronze is a noble metal with a range of potential for galvanic corrosion much more acceptable than brass.
A lot of those fittings are also available in marelon which is compound made of reinforced polymer and additives. Unfortunately their product does not fit in our case size wise. Too bad. Seems the way of the future.
