Aluminium galvanic corrosion

turrican

Well-Known Member

Posts

234

• May 22, 2019

• #1

Quick question on aluminium galvanic corrosion. Will the corrosion stop if it's isolated and not in contact with other metal, or will it continue spreading like rust and need to be cut out?

 

Henry_b

Think outside, no box required.

Posts

15,509

Location

somewhere else

• May 22, 2019

• #2

Depends how bad it is..

Wire wheel it smooth/no flaky bits and repaint and isolate from steel if possible..

 

mick the builder

Well-Known Member

Posts

5,901

Location

Sligo,Wild West of Ireland.

• May 23, 2019

• #3

When i rebuilt my 110, i did as Henry b suggested and also used thin EDPM rubber in between any ally and steel.

 

J

j_g_uk

Well-Known Member

Posts

229

Location

Fareham

• May 23, 2019

• #4

I work in the marine industry some of the time so know a little about corrosion and galvanic reactions. Galvanic reaction in the context being discussed here requires two metals separated on the galvanic scale (the further the separation the greater the effect) connected together electrically (ie fastened together without insulation) with an electrolyte (ie salty water) touching both metals.

Insulating one metal from the other helps and gaskets or a jointing compound also helps. The industry stuff used widely is Duralac https://www.s3i.co.uk/duralac-jointing-compound.php=EAIaIQobChMIu_rXkYmx4gIVzJPtCh3Atwq-EAAYAiAAEgJwS_D_BwE.

Similar stuff is used in aircraft construction and repair.

 

turrican

Well-Known Member

Posts

234

• May 23, 2019

• #5

I've got some rubber tape to insulate the different metals and paint the metals to provide another barrier.
My question is will the existing aluminium corrosion continue to corrode even after being isolated for the other metal?

 

J

j_g_uk

Well-Known Member

Posts

229

Location

Fareham

• May 23, 2019

• #6

How will you insulate the fastenings? Electrical connection plus dissimilar metals plus electrolytes equals corrosion sooner or later. Ensuring there’s no water or dampness left or trapped helps and the paint will slow things down.

 

Discodevon

Well-Known Member

Posts

1,454

• May 23, 2019

• #7

I would say once stuff like that starts you can only slow it down, remember rust and aluminium corrosion needs oxidation to survive so depriving it of air will virtually stop it

 

turrican

Well-Known Member

Posts

234

• May 23, 2019

• #8

I was looking into using duralac for isolating the fasteners.

I hoped that removing the dissimilar metal from the equation would stop any existing corrosion from spreading.

 

Disco1BFG

Well-Known Member

Full Member

Posts

6,316

Location

Buxton

• May 23, 2019

• #9

turrican said:

I was looking into using duralac for isolating the fasteners.

I hoped that removing the dissimilar metal from the equation would stop any existing corrosion from spreading.

Click to expand...

Removing dissimilar metals on a LR is a bit of a tall order .... IME, the only way to stop existing corrosion is to abrade back to clean metal and etch prime immediately ... This tends to work 90% of the time .... when the corrosion comes back - it's usually on a smaller area, so just rinse and repeat

I've no experience of duralac - but use Bilt Hamber Dynax S-50 cavity wax, and get good results