Google "grounding to aluminum" and read what you find. You just got bad info from McCarthy. But then he's all about contradicting.
If you google "galvanic corrosion, you'll find on wikipedia this:
http://en.wikipedia.org/wiki/Galvanic_corrosionExcerpts from this article that pertain to galvanic corrosion and this issue: NOTE - in this context, moisture acts as the electrolyte.
Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially to another when both metals are in electrical contact and immersed in an electrolyte. The same galvanic reaction is exploited in primary batteries to generate a voltage.
Dissimilar metals and alloys have different electrode potentials and when two or more come into contact in an electrolyte a galvanic couple is set up, one metal acting as anode and the other as cathode. The potential difference between the dissimilar metals is the driving force for the accelerated attack on the anode member of the galvanic couple. The anode metal dissolves into the electrolite, and deposition is formed on the cathodic metal.
The electrolyte provides a means for ion migration whereby metallic ions can move from the anode to the cathode. This leads to the anodic metal corroding more quickly than it otherwise would; the corrosion of the cathodic metal is retarded even to the point of stopping. The presence of an electrolyte and a electronic conducting path between the metals is essential for galvanic corrosion to occur.
Metals (and their alloys) can be arranged in a galvanic series representing the potential they develop in a given electrolyte against a standard reference electrode. The relative position of two metals on such a series gives a good indication of which metal is more likely to corrode more quickly.
There are several ways of reducing and preventing this form of corrosion.
* One way is to electrically insulate the two metals from each other. Unless they are in electrical contact, there can be no galvanic couple set up. This can be done using plastic or another insulator to separate steel water pipes from copper-based fittings or by using a coat of grease to separate aluminium and steel parts.
It is also possible to choose metals that have similar potentials. The more closely matched the individual potentials, the lesser the potential difference and hence the lesser the galvanic current. Using the same metal for all construction is the most precise way of matching potentials.
The compatibility of two different metals may be predicted by consideration of their "Anodic Index". This parameter is a measure of the electrochemical voltage that will be developped between the metal and gold. To find the relative voltage of a pair of metals it is only required to substract their Anodic Indexes.[8]
For normal environments, such as storage in warehouses or non-temperature and humidity controlled environments, there should not be more than 0.25 V difference in the "Anodic Index". For controlled environments, in which temperature and humidity are controlled, 0.50 V can be tolerated. For harsh environments, such as outdoors, high humidity, and salt environments, there should be not more than 0.15 V difference in the "Anodic Index". For example; gold - silver would have a difference of 0.15V being acceptable [9][page needed]
Often when design requires that dissimilar metals come in contact, the galvanic compatibility is managed by finishes and plating. The finishing and plating selected facilitates the dissimilar materials being in contact and protect the base materials from corrosion.
Anodic index[9][page needed] Metal Index (V)
Most Cathodic
Gold, solid and plated, Gold-platinum alloy -0.00
Rhodium plated on silver-plated copper -0.05
Silver, solid or plated; monel metal. High nickel-copper alloys -0.15
Nickel, solid or plated, titanium an s alloys, Monel -0.30
Copper, solid or plated; low brasses or bronzes; silver solder; German silvery high copper-nickel alloys; nickel-chromium alloys -0.35
Brass and bronzes -0.40
High brasses and bronzes -0.45
18% chromium type corrosion-resistant steels -0.50
Chromium plated; tin plated; 12% chromium type corrosion-resistant steels -0.60
Tin-plate; tin-lead solder -0.65
Lead, solid or plated; high lead alloys -0.70
2000 series wrought aluminum -0.75
Iron, wrought, gray or malleable, plain carbon and low alloy steels -0.85
Aluminum, wrought alloys other than 2000 series aluminum, cast alloys of the silicon type -0.90
Aluminum, cast alloys other than silicon type, cadmium, plated and chromate -0.95
Hot-dip-zinc plate; galvanized steel -1.20
Zinc, wrought; zinc-base die-casting alloys; zinc plated -1.25
Magnesium & magnesium-base alloys, cast or wrought -1.75
Beryllium -1.85
Most Anodic
CONCLUSIONS
The anodic index of copper (the wire) is -0.35v. The anodic index of stainless steel is -0.50v - A difference of 0.15, OK per the above discussion. Note the anodic index of cast aluminum is -0.95v - a difference of 0.60v when in contact with the copper wire - HIGH GALVANIC CORROSION IS PREDICTED.
As I said - you can reduce or prevent it by coating the connection - and I use electrically conductive compounds that are made for connecting to aluminum.
I'll make a note, when flying into NH, not to let McCarthy touch my airplane.
Yes that's all very nice, except that nowhere does it say that you cannot electrically bond to or through aluminum. I'm intimately familiar with galvanic corrosion because I'm a structures specialist. I've seen lots of it.
And you won't make it here anyway because your electrically bonded through it's aluminum structure (at literally HUNDREDS of places) aircraft is going to crash before it get here.
Seriously Marky-Mark, just go ahead and post my full address like you did before. I know you want to and I really don't mind.
