Aluminium oxide and zinc oxide are very hard chemicals, and attach very well to their base aluminium and zinc metals underneath. Not only that, the molecules of the oxides are a little bigger squeeze together forming an impenetrable skin..

Polishing will remove the protective oxide layer, repeatedly eventually removes the galv.. thu on an alloy boat ...

 put it this way will take a long time and quite a few polishing wheels to wear thru the solid hull.

We polished a lot of old school V8 valley covers, manfols , carbs, trans and wheels over the yrs.. some so bad they where solid white oxide.

 When polishing or cutting, machining different metals require different cutting fluids.. aluminum is kero.

We us  white stainless steel polishing rouge..

 Also aluminum is a little different to polish than most other metals.. other metals is more fine 'sanding' of rough layer...

 Aluminum one gets heat into it, as you move along slow building and keeping heat.. quite hot to the hand, keeping  the top layer of molecules melt into the tiny pits and scratches...

 But id there is deep corrosion, pits scratches...start with a sander .. or if real bad a file

 When sand (or file) .. and this goes right thru to poolishing stage.. watch real close.. nearly take out the pit/ scractch. Do not scratch the bottom of the pit, not quite.

 Then move to a finer wet and dry paper.. then finer, by this stage you will be at 400 or 600 grit... When have a very faint pt/ scratch left.. then buffer, rouge to finish taking it out and the scratches from the sand papers.

Once polished, cleaned down with kero, can choose to clear coat or quaity  car polish  depending on end use..

3 or 4 layers  a day apart of polish is good for wheels, manifolds etc..  2 pot clear coats  for trans carbs etc  and boat..

 Now thats a hell of a lot of real dirty , messy , time consuming work...

Seriously consider a wrap...

 but check out the surface prep for wrap...never done it ,therefore never found out about it, so dont know.

 A good wash down, after every trip, using a quaity detergent, and a rinse with a polymer added.. designed for purpose , from new goes a long way.

 Its called maintance, regular maintance.

 mentioned in old posts..

Reading labels (out of interest) on the products Tagit refers to are a mixture of weak acids including citric and phosphoric.

 I was hesitent to mention the acids.. as used on carbs, trans box etc but never on a boat...and not my boat..and knowing alloys come in a lot different formulas, could not recommend doing so..

 In saying that.. if was my boat I would try a little in a cnr somewhere have a play.

While at it check out what is in rust kill.. the stuff without epozy additives.. and also gelcoat cleaner...

 That brown 'stain ' on the hull of a glass boat.. maybe also and alloy boat..

 Rust killer.. couple caps in a bowl of water, a rag and simply wipe on and leave.. no need to rinse

BIG WARNING here

 these acids DO NOT let drip onto the galv of your trailer.. eats the crap out of the thin layer of zinc...

 So wet the rag, wring well out and wipe.. I dont bother with gloves.. the acids are to weak.. like coke or lemon juice

 Im a fan of glass, inthe approiate conditions.

But again for long term condition/ appearance glass also needs ruotine maintace and protection from eliments/ sun espec the upper deck / cabin..

 And down side glass.. if not well maintained and going to cut polish.. that cuts back the gelcoat.. do that a few times and the gelcoat starts to get thin

 An alloy boat is solid alloy

 

Me, several times

We own an alloy boat built and painted (properly) in 1987 and 90% of the paint is still in really good shape. 

There is localised paint loss in the areas you would expect like the leading edges of the bow.