There has been quite a lot of activity in the Samba Vanagon forum on the subject of stainless steel cooling lines causing dissimilar metal corrosion in the aluminum alloy engine. About a week ago I decided to do a little experiment to see if I could detect any visible corrosion on a bit of aluminum connected to stainless steel, both in shared electrolyte of engine coolant.
The stainless is 304, the aluminum is 6061. Both samples are 0.125″ X 0.750″ and immersed in the coolant to approx 2″.
The coolant in a 50/50 mix of OAT based coolant and distilled water.
I did a casual buffing of both samples with tripoli, and then degreased. The buffing was to allow any corrosion to be more visible. In the picture, the aluminum is on the right.
The samples are connected by tinned copper wire.
Ambient temp in the lab, I mean the barn, ranges from 7 C to 10 C.
Initial measurements between the unconnected samples in the coolant was, 150 microAmps and 540 milliVolts.
Experiment started at 6:30 pm, pacific time, October 26 2010.
I’ll leave it undisturbed for a week or so, then take pics of the metals.
It will be interesting to see if anything happens
Nov. 2 1220 hrs – I pulled the metals out of the jar and rinsed off coolant. The aluminum looks pretty good. I don’t know if the pic shows it but there is a very slight haze on the surface.
I replaced the coolant with tap water (well water, pretty hard), and set the expt. up again, same conditions as before. Initial readings are:
326 mV and 195 microAmps between the 2 samples.
(I don’t know why wordpress is sticking the “I” up there to the right of the image… I have tried to get it back down, the html looks right to me, but…)
Update, Nov. 4, 2010.