Anti-corrosion
How to deal with aluminium corrosion
The problemIn most surroundings - inside or in the open air - aluminium has a very high resistance to corrosion . One reason for this is that Aluminium is covered spontaneously by a thin but effective coating of oxide which protects the Aluminium from further oxidation. The Aluminium oxide is impermeable and is integral with the base metal. If the coating of oxide is damaged mechanically this coating will be renewed immediately. Generally alloys with more than 0.5% copper have a worse resistance to corrosion and they should not be used in unprotected.
To build the RV-7A, mostly 2024 aluminium is used. This is an alloy containing 5% of copper, and traces of iron, manganese, magnesium and chrome. All the skins are Alclad this 2024 alloy coated with a thin layer of pure aluminium.
If the thin pure aluminium layer is undamaged the skin will be protected against corrosion. But the non-Alclad parts need to be protected, they contain at least a 5% of copper.
During building itâ??s quite difficult not to damage the Alclad , thus I think the whole structure has to be protected.
The solutions
There are a few possibilities to protect aluminium, but some are not suited for an amateur builder due to hardware needed or price. For more details see here : http://aluminium.matter.org.uk
The amateur builder is left with chemical processes that are easier to work with. Some informations here (in French) but a websearch will yield a lot more answers in english.
I have chosen a relatively simple method, trying also to produce the least possible toxic waste.
The products are from Diatex.
The problemIn most surroundings - inside or in the open air - aluminium has a very high resistance to corrosion . One reason for this is that Aluminium is covered spontaneously by a thin but effective coating of oxide which protects the Aluminium from further oxidation. The Aluminium oxide is impermeable and is integral with the base metal. If the coating of oxide is damaged mechanically this coating will be renewed immediately. Generally alloys with more than 0.5% copper have a worse resistance to corrosion and they should not be used in unprotected.
To build the RV-7A, mostly 2024 aluminium is used. This is an alloy containing 5% of copper, and traces of iron, manganese, magnesium and chrome. All the skins are Alclad this 2024 alloy coated with a thin layer of pure aluminium.
If the thin pure aluminium layer is undamaged the skin will be protected against corrosion. But the non-Alclad parts need to be protected, they contain at least a 5% of copper.
During building itâ??s quite difficult not to damage the Alclad , thus I think the whole structure has to be protected.
The solutions
There are a few possibilities to protect aluminium, but some are not suited for an amateur builder due to hardware needed or price. For more details see here : http://aluminium.matter.org.uk
The amateur builder is left with chemical processes that are easier to work with. Some informations here (in French) but a websearch will yield a lot more answers in english.
I have chosen a relatively simple method, trying also to produce the least possible toxic waste.
The products are from Diatex.
- Degrease
- Wash with sotchbrite
- Degrease with Diatex surface cleaner
- Intergard 90 : Diatex two-part epoxy primer
- Finishing paint as desired
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