My main experience is with aluminium - most commercial
vessels and the larger end pleasure vessels are now made from it. It would now be my probable choice if we were to ever have another boat built for ourselves (unlikely
Ignore all the stuff people talk about corrosion if you park next to steel
piles, other boats, etc but not connected to shore power
(commercial boats and superyachts do so all the time with not a care). For when you are connected to shore power
ensure the boat you are looking at uses a properly installed marine
If the boat is 10 or more years old have a close look for any corrosion issues under insulation or where debris (dust, etc) may be lying on longitudinals against the plating, etc - a problem there may indicate an alloy problem. If possible check the bottom of the fuel tank
, pitting is common where water
may collect in the lowest point - not normally a big problem if accessible for repair (crop and weld).
Painting should not be a problem - if you are faced with painting bare aluminium usual is coarse power sand back to remove the oxide layer then straight on with the paint manufacturer's recommended epoxy
primer and undercoats. For any repairs
or recoating get a paint specification from a reputable marine
paint manufacturer (International/Interlux, Jotun, etc) they are normally very helpful. Castings of aluminium may be less resistant to corrosion.
As already said it should be insulated inside above the waterline for both control of noise
(need not be so outside of the accomodation areas but, as mentioned by another, may be useful under the stern counter to stop the noise from wave slap if in a slip stern to the wind). In my view the prefered insulation should be a sheet closed cell foam such as Korex or Armaflex or else sprayed foam - if the boat has a porous type insulation used (eg fibreglass or mineral fibre panels) then I think I would walk away from the boat unless I knew for sure the condition of all the plating behind.
I would suggest having someone who is professionally knowledgable and familiar with aluminium boats check it out for you. Like steel
boats one can often get a good idea of what the overall quality of the boat is likely to be if one has an eye for boats in just the detailing of its construction and fitout - some you can walk away from without even going on board. Ensure that as it is not a new boat there have not been adventurous amateur escapades into its electrical and galvanic protection systems (the DC system, including engine
, should preferably be one entirely isolated from the hull and with some means of monitoring that the isolation has not been compromised).
As others have said, all materials have their problems. But I would suggest that now with better coatings which stay on and modern alloys (both of which may not apply to an oldish boat though) and its widespread use through the commercial and superyacht building industry greatly increasing the knowledge of it, aluminium is now probably the material with potentially, if properly built, the very least problems.