Strange corrosion on aluminium

[Fazerruss]

This is a weird one. It's an aftermarket suspension top mount for a Nissan Skyline that someone has asked me to have a look at. It has separated like steel does when it rusts. The oxide in the crack is rock hard and can't be scraped out.



He assumed I would fill it with weld but this is going in the bin and I'll make a new one.

 

[Dev]

Galvanic corrosion?

 

[Fazerruss]

Possibly, but it's odd how the aluminium has separated along its circumference.

I've never seen anything like this despite playing with all sorts of aluminium parts from extreme environments. Jet skis, speed boats ect.

 

[tom2207]

Aluminium oxide is harder than steel ,, its whats used on some flap discs and things like that
and often as a diamond substitute .


dont try putting a lump in a ring or er indoors wont be happy though ,,, just thought Id mention it.

 

[Brad93]

General corrosion being on a car, galvanic from the stainless fasteners, and that has resulted in stress corrosion crack or stress fracture where the alloy has work hardened.

 

[grim_d]

It's called exfoliation corrosion and is a subtype of intergranular corrosion, something about the grain boundaries causing localised galvanic corrosion in which gives rise to the "layers" or "delamination"

Common on aircraft sadly, seen it numerous times.

More HKS rubbish with dissimilar metals, full header back stainless HKS exhaust on the Subaru...hangers are mild steel.

 

[Brad93]

It's called exfoliation corrosion and is a subtype of intergranular corrosion, something about the grain boundaries causing localised galvanic corrosion in which gives rise to the "layers" or "delamination"

Common on aircraft sadly, seen it numerous times.

More HKS rubbish with dissimilar metals, full header back stainless HKS exhaust on the Subaru...hangers are mild steel.

text book. A good one is Fontana and Green. It goes in one ear and out of the other with me unless I’m using the information every day.

 

[hotponyshoes]

I have got some 2000 series alloy billet that got wet.
The corrosion on that is nothing like as extreme but it does seperate into layers like that.

 

[bigegg]

Ive seen sonething similar with occlusions in cast aluminium.
Maybe a manufacturing fault (allowing stuff in), rather than just an environmental issue?

 

[ronan]

It's called exfoliation corrosion and is a subtype of intergranular corrosion, something about the grain boundaries causing localised galvanic corrosion in which gives rise to the "layers" or "delamination"

Common on aircraft sadly, seen it numerous times.

More HKS rubbish with dissimilar metals, full header back stainless HKS exhaust on the Subaru...hangers are mild steel.

Done deliberately so when the exhaust falls off the car, you have to fork out for a new one ?

 

[colnerov]

Done deliberately so when the exhaust falls off the car, you have to fork out for a new one ?

That's very cynical.

 

[Mr Roo]

Done deliberately so when the exhaust falls off the car, you have to fork out for a new one ?

or possibly considered throwaway because most of the louts fitting that sort of kit will wrap the motor round a lamppost within a year or so anyway!!

 

[grim_d]

Done deliberately so when the exhaust falls off the car, you have to fork out for a new one ?

I'm a big cynic bit it's on a JDM car, installed in Japan where it would probably never corrode...unless they knew it was coming here....