Life expectancy of an aluminum gas tank
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aheny
Well-Known Member
As a corrosion technologist, I can speak to the hot water tanks. The reason they have mostly consistent shelf life is the heat, which is one of the 4 factors directing controlling corrosion rate. In addition to this the temperature also contributes to hydrogen embrittlement, this causes the metal to become brittle over time as it is constantly heated, eventually cracking, causing failure.
An aluminum fuel tank is actually quite well protected from corrosion internally as long as you don't let water accumulate and sit too much. Your main concern is going to be galvanic corrosion, dissimilar metals in contact such as screws/bolts. Outside of the tank is another story though, here you are more likely to have the tank in contact with a soggy electrolyte, such as wet wood, possibly salty, which can cause external corrosion. However, this corrosion will be plainly visible to inspection.
The short answer is no, there isn't a definite shelf life as long as you control corrosion of the inside of the tank, the outside of the tank, and wherever other metals contact it.
An aluminum fuel tank is actually quite well protected from corrosion internally as long as you don't let water accumulate and sit too much. Your main concern is going to be galvanic corrosion, dissimilar metals in contact such as screws/bolts. Outside of the tank is another story though, here you are more likely to have the tank in contact with a soggy electrolyte, such as wet wood, possibly salty, which can cause external corrosion. However, this corrosion will be plainly visible to inspection.
The short answer is no, there isn't a definite shelf life as long as you control corrosion of the inside of the tank, the outside of the tank, and wherever other metals contact it.
scott craven
Well-Known Member
Most water heaters are glass lined .over time the lining will break down exposing bare metal.
The water quickly goes to work on the bare metal eventually rusting through and causing a leak.
aheny
Well-Known Member
Absolutely Scott, the internal coating also provides a temporary (predictable) relief from corrosion. Once in contact with the metal though, its the specific activities of the heat, rather than the presence of the water, which causes the corrosion. A cold water tank would have a completely different corrosion rate, and would not fail due to embrittlement.
when engineering coatings and cathodic protection for water pipes and vessels, if the water is only ambient temperature, you can usually get more than 30 years design life with very minimal protection. In many cases, we don't even use protection for municipal lines.
when engineering coatings and cathodic protection for water pipes and vessels, if the water is only ambient temperature, you can usually get more than 30 years design life with very minimal protection. In many cases, we don't even use protection for municipal lines.
Peahead
Well-Known Member
So as far as moisture/dampness on the outside of a aluminum fuel tank ...if you have a cockpit deck over fuel tank/s and that deck (self bailing) is laid in sections that are screwed down and edges sealed ( inspection plates as well ) but they do leak a bit when it rains and after a fresh water hose down, can this water leaking through down onto the aluminum fuel tank compartment cause a serious acceleration of fuel tank corrosion ? I think this situation is pretty common as I really doubt there are many cockpit deck floors that are always 100% waterproof - drainage down to the bilge is provided in the fuel tank spaces so seems moisture is expected there rather than unexpected ?? . Condensation moisture on the underside of the floor dripping onto the fuel tank is also something that I understand happens ....is this avoidable or even necessary to avoid...or all part of why a fuel tank has a expiry time, eventually.
aheny
Well-Known Member
Peahead, you need to look at the tank as two separate things. Internal corrosion is unrelated to external corrosion. As for as external corrosion goes, I would be most concerned about an iron based screw touching the tank in a wet piece of wood/carpet. If its strictly sitting in sopping wood, it will accelerate the external corrosion, but it will be evenly spread out over the entire tank, small corrosion cells here and there causing minor damage. However, a screw touching the tank would quickly become a cathode, making the tank near it act as an anode, causing pitting around this location. This is where you could have a premature tank failure.
Dry is best, stay on top of water inside the tank, and take care to not let other metals touch the tank accidentally, and you'll be ahead of 99% of the corrosion.
Dry is best, stay on top of water inside the tank, and take care to not let other metals touch the tank accidentally, and you'll be ahead of 99% of the corrosion.
Cmiles
Active Member
Corroded and started leaking
Rayvon
Well-Known Member
I have the same year boat (1994) and mine was replaced 2 years ago before I bought it.Very few bilges are dry as hard as we try and the underside of the tank is probably sitting on ships felt or similar material that can remain wet.Hopefully it's fresh water and not salt as this would accelerate the corrosion process.I think 20 years is a decent life expectancy for an aluminum tank,although others will disagree,especially if theirs is hard to remove.My last boat had a plastic tank and never had a problem,it was a 1989.
