What causes blisters on side of caravan aluminium?
Answers:
rust spots under the paintwork
Damp probably
rust
If it's aluminium it will form a dull oxide layer that actually protects the material from further oxidation. It won't actually rust (that term is reserved for iron/steel). It's possible that a laquer covering the aluminium is blistering due to overheating by solar radiation. Aluminium can get quite hot when exposed to sunlight. If the aluminium is dull underneath the blisters and shiny elsewhere that could be the cause.
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