I've read statements that say, "Don't ever have to worry about rust because of aluminum body." What I've been able to glean from googling is that the entire frame and body are indeed all aluminum on the 2004+ XJ8's. Does that mean there are no steel parts?

In contrast, on my two Saturns there are fiberglass panels, but the hood, roof, and trunk are steel. What about the XJ8? And does the aluminum actually translate into no rust?

I have a couple spots where the paint has bubbled. At first I thought it was from underlying rust, but after closer inspection I think it's just that the paint didn't keep its adherence to the metal. Anyone else experience this? Thanks!

 

Well actually Aluminum does rust but most people do not think of it as rust as it is different from Iron or steel and it looks different it pits and the rust looks more like white dust.

But the good news is it takes a lot longer and most aluminum has a outer layer on it that slows it down extensively also the primers are such that they adhere better to the metal.

The only other problem that can occur is if the metal is exposed to other metals that react to the aluminum this can cause a problem, but in the design of the car this does not happen.

I know most of this as I have been an aircraft engineer and looked after aircraft fuselages and there repairs for many years and there are a lot of 70 and 80 year old aircraft still in perfect condition around.

 

From the January 2013 X350 feature in Jaguar World magazine : The car is comprised of sheet aluminum, aluminum castings and aluminum extrusions with almost 3,200 rivets...The rivets are steel but are protected with a zinc and tin coating...due to the mixing of metals some "galvanic" corrosion can occur especially when a corrosive electrolyte like salt water is retained by the boot lid seal... Additionally water may get behind the paint and cause bubbling, apparently this is cosmetic and not structural.

 

What does happen to aluminium, and is probably the cause of your paint bubbling, is a form of corrosion, filiform that happens if the aluminium had some steel flake or other contaminant on it prior to painting. The aluminium apparently oxidises to protect itself causing the blisters in the paint. It is usually reasonably firm. Jaguar was fixing cases when it occurred.

 

These cars do suffer from filiform or crevice corrosion. Aluminium is funny stuff; exposure to air is OK unlike steel, whereas exclusion from air with water present, (plus salt) is harmful. SO you can get filiform starting in crevices and as the aluminium corrosion products tend to be greater volume than steel you see horrid bubbling under the paint.

Look at: -

- leading edge of trunk lid. It creeps round from the underside where the lip on the screen seal has rubbed paint away. Cut this lip off after rectification!!

- above "Jaguar" plinth on the trunk lid. It creeps out from the crevice above the plinth where the trunk lid curves round. This was due to bad assembly line technique and doesn't usually appear on later cars

- corners of doors. This one is a bit of a puzzle as it doesn't seem to have crept round but it has gotten there somehow from the crevice formed by the door rubber seal and the door pressing.

- fender edges. Only high mileage cars usually get creep-out from the edge, but it's caused by fretting between fender metal and the wheel arch liner

BTW,I've never seen galvanic corrosion from the riveting, not yet anyway. I think it is a red herring to be honest, unless somebody can post up a picture.

 

Thanks for all the helpful information!

 

May not even have applied to enough Jaguars in enough venues to actually matter.

Anecdotal evidence is that VW/Porsche/Audi (much of the A8-L, & alleged-Bentley, plus parts of the VW Phaeton) had some issues with galvanic effects.

They also had much the same paint issues w/r panel-edges, around trim, and with trace iron transfer from forming dies. But VW's approach to use of aluminium is a different one from jaguar's in many more respects than just fastener selection. Closer in some details to the old Ferrari Mondial's approach.

The major aluminium players have been up to their anatomy in assisting automakers to get it right and increase market, given how aircraft are trending more and more to carbon-fibre.

AFAIK, all -hands had learned what MUST be avoided pretty well by third year of production if not the second year.

Or so I hope and trust on my own X350.....