Tel wrote: ↑Tue Mar 23, 2021 5:49 pm The particular OP looks to be a combo of oxidisation and possibly some coolant attack. The reason I say coolant, is the depth of scour in the metals' surface.
The only way to stop ally oxidising is by sealing it on day one. By seal, I don't mean your fancy automotive sprays, you require something that 'films' and provides an effective seal against oxygen.
For coolant, then you need to find the source of the leak.
For the past 30 odd years I have been experimenting on many bikes and cars.
I have recommended marine sprays such as Quicksilver Corrosion guard within many posts on this forum.
JLR use Würth products on the replacement underbody braces to seal the already coated steel surfaces.
You need that understand that automotive products are pretty lame at what they claim. Marine and aerospace though you not only go up in price, but you get a product that actually does what it is supposed to do, effectively.
I was fortunate, having bought the car brand spankers, on the journey from the dealer to home, I stopped at my local friendly garage and spent a couple of hours sealing everything, top and bottom. Subsequently it's like the day it left the showroom. The same can be said for my bikes, of which he oldest is 30 plus years and the ally work is as new.
Several ways to clean it up - You need acid. I would suggest Alubrite (https://www.chemwash.co.za/DataSheets/alubrite.html)
It works perfectly, and you need to be cautious of surrounding materials, so be handy with the hose to neutralise.
Once clean, start the engine to dry and 'seal' - Alternatively you could just leave it, but it doesn't look particularly pleasing to the eye.
Good preventative work you did there by sealing everything, top and bottom, when you first bought your car. I think you’ve previously said that your car is kept in the garage with controlled climate so that’s also helping to prevent corrosion etc.
The ‘Alubright’ Deoxidiser that you mention appears to be excellent for this sort of work......good tip that! It dissolves corrosion, removes white oxidation within minutes and leaves a bright, as new finish on dull grey engine blocks. This can be sealed in with ‘Jet Laq’.
Had a quick search and found these......
https://www.frost.co.uk/alubright-deoxidiser-500ml/
https://www.frost.co.uk/let-laq-1200-no ... uer-250ml/
After reading some of the information in this topic and researching ‘aluminium corrosion’, my concerns have been eased. This is due to the fact that as a result of the oxidation process, the aluminium oxide film which forms on the metal surface acts as a protective barrier and helps prevent further corrosion. Also, in most environments, the rate of corrosion of aluminium decreases rapidly with time.
If I did decide to remove the corrosion, I’d use ‘Alubright’ and then ‘Jet Laq’ to seal it. However, there are some areas which are difficult to get at so they would probably have to remain as they are.
Thankfully, the corrosion (or should I say protection) on the rear of the engine block and bell housing etc is not in a highly visible area.