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My five door hatchback Laguna RTi facelift has many aluminium components in the sports engine compartment, etc. whose surface is suddenly being converted into white powder. I attribute this corrosion to the recent installation of many condensing boilers on my housing estate.

Condensing boilers have one drawback and that is their ability to create corrosive exhaust gas. This acidic exhaust gas is a by-product of the high efficiency combustion process inherent with all condensing boilers. The exhaust gas is not a pure acid but has just enough of a low pH level to corrode anything other than plastic or stainless steel. The condensing exhaust gas is slightly acidic with a pH level of three to five. Basically pure clean water has a pH level of seven which is considered neutral, anything with a pH of less than seven is considered acidic and is corrosive while anything with a pH level greater than seven is considered alkaline and is not corrosive.

Has anyone encountered a similar problem with their vehicle? Painting the components that do not get hot seems a good remedy. However, the Laguna RTi intake manifold gets hot and I am looking to apply a temperature resistant clear paint so that the engine’s visual appearance is unchanged. Can anyone recommend a temperature resistant clear paint?
 

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Super Moderator Technical Supremo Platinum Member
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If I may correct some of your assumptions.

Both acid and alkali will corrode aluminium, caustic soda loves it for instance.
Condensing boilers typically produce less harmful emissions then traditional flues, carbon dioxide, carbon monoxide and water are the main emissions.
Aluminium needs no corrosive agent, it readily combines with Oxygen in the atmosphere forming a skin of Aluminium Oxide which is passive.
But engine fumes, condensation, heat cycling and the like can create a corrosive atmosphere akin to a tropical rain forest. Hence the white powder.
A stiff brush will dislodge most if it is getting to you, not a wire brush as this will scratch.
 

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Technical Supremo, Platinum Member
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Aluminium that is exposed to the air does form white powder rather quickly ..... I had this on my aluminium hubcaps back in the seventies. Unless the surface is sealed by either polish or lacquer it will keep returning. Incidentally iirc the white powder actually protects the remaining metal underneath from further corrosion...... it justs looks unattractive.
 

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+1 for aluminium oxide, oxygen from the air.

The Japanese motorcycle manufacturers used to lacquer their showy alloy engine parts. I presume they still do.
 
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