aluminum heads and electrolysis

[Diesel Dude]

I was speaking with a mechanic today about the design of the duramax heads and the stainless steel injector inserts .he stated that from experiance with other aluminum heads they are a pain to dissassemble.with regards to the stainless steel injector inserts of the duramax,my question is what is the incidance of elctrolysis between stainless steel and aluminum.as the mechanic attributed the difficulty with using dissimular metals being caused by electrolysis .also would it be a bad thing if the inserts were adhered to the head essentialy bonded with electrolysis? could this property be a benefit and maybe used in the manufacturing of the heads like induction hardening?

[Viking]

I feel that if the engineers that put this engine together did not consider the electolyis problem, we will have a lot more too be concerned about!!!!

[Viking]

Make that "electrolysis"

[Diesel Dude]

I wanted to add to my privious statements:what about the differant expansion rates of dissimular metals in thermal conditions and would this offset electrolysis action?

[mackin]

What does hair removal have to do with injector cups???I can see the head correlation...... tongue.gif

Isn't ""electrolysis"" used in the production of raw Aluminum????
I think I read that some where....I guess what your referring to is oxidation between injector cup and head and using "electrolysis" as a form of cleaning like in cleaning rusty bolts???? With a "electrolyte"????

I quit.......Just wanted to get the hair thing in any way......

MAC :D

[Kennedy]

Unless I am mistaken, stainless (not that 409 crap) will not cause electrolysis with aluminum. These sleeves would be a 300 grade for sure. Now mild steel and low grade is another story. On aluminum trailers some have had the misfortune of not isolating the steel and aluminum :eek:

[SoMnDMAX]

304 series stainless and aluminum will not react with each other.

[mackin]

So true about Aluminum and steel......I've beaten many a alum rim off a steel brake drum....... :eek: This is probably what the mechanic was referring to......

MAC

[ 10-24-2002: Message edited by: mackin ]</p>

[Amianthus]

This is one thing I know a little about (I work in an aluminum plant, http://www.chart-ind.com/p_heatexchangers.html ).

What he is talking about is called galvanic corrosion. That type of corrosion is when you have two metals that have differing electrostatic potentials in electrical contact and in an electrolytic solution. What happens is the free electrons from one metal travel through the solution to the other metal. This weekens and corrodes the metal from which the electrons came.

Aluminum and steel have a huge difference in electrostatic potentials and so the aluminum will corrode pretty quickly. Aluminum and stainless have a closer potential and so the corrosion will not be as fast. Of course, the electrostatic potential depends on the alloy of aluminum used and the stainless alloy used. We bond aluminum to stainless all the time here for transition joints and for attachments to the heat exchangers. Because of the similar potentials of the two metals, corrosion can be considered negligable.

As for using this combination in the Dmax, I'm sure the engineers took this into consideration when they chose the material they would use in the injector sleeves. I don't see this being a problem with normal use. If they didn't, then they are idiots and you guys are left with a problem.

[hoot]

And let's not forget about the millions of engines in service today with iron blocks, aluminum heads and steel inserts.

[D-max Man]

These are "wet sleeves" which means that they are surrounded by coolant (to cool the injectors).
If you perform proper cooling system maintenance, the additives in the coolant will prevent this from happening.

[Diesel Dude]

hey,you guys are great!all that information in less than 24 hours.what I really want to know is how did that guy know about my hair loss, amazing.