Crusty windows
Q
I have a Moody 31 built in 1989. My aluminium windows show signs of white oxidation. I am never keen to fix things that ‘ain’t broke’, but appreciate maintenance helps to keep things in good order.
The windows do not leak at the moment but it’s preferential to carry out any work before they start to leak and cause more problems. Can you advise as to the sort of options that are available? Neil Daniel, by email colin BRoWn Replies: Pure aluminium is very low on the galvanic scale and not used very much. Various other metals are added to give more strength and durability. Even as an alloy aluminium is protected from the environment by an oxide film that forms almost the instant that the bare aluminium is exposed. This passive layer is made thicker by anodising, an electrochemical process that creates a thicker oxide layer than that which forms naturally. This is the surface that you see on your window frames and on most aluminium alloy masts and spars.
The white residue under the rubber seal may be salt or it could also be aluminium hydroxide. Both require water to be present so your windows are letting some water in. I think salt is more likely as hydroxide is more usually associated with poultice corrosion where a wet and absorbent substance such as fabric or wood is held wet against aluminium. I suspect that the seals round your window frames are ageing and that there is a slow weep of water that evaporates as fast as it enters and leaves a salty residue.
Wipe the residue off with a warm, damp cloth for now, but removing the windows to fit new seals should be in your medium term plans.