Aluminum parts in cars getting corroded?

[felixc]

Hi,
are cars with aluminum parts doomed to the scrapyard earlier than regular cars, because of galvanic corrosion?
My brother is a mechanics at a Ford dealer, and he says that cars like the Lincoln LS, with aluminum parts in its suspension, is hard and costly to repair when aluminum parts are involved, they are corroded so badly. (of course in the short term it makes the dealer happy) When regular maintenance involves aluminum parts, many of these parts must be replaced, there's just no way to remove them without damage. I'm in Montreal, and the environment is very salty during winter.
I remember using aluminum rivets to hold a cable on an older car. The rivet has been eaten within a year.
Is aluminum a wave of the future in cars, or just another way to a quicker obsolescence? Will a cheap all-steel car be safer after 10 years than a high-tech car with aluminum parts? (too bad, I like the Lincoln LS)
Felix

 

[mcguire]

The culprit isn't galvanic corrosion. It is the quite poor corrosion resistance of aluminum. Carbon steel cars had terrible performance vis-a-vis corrosion until they began to use electro-galvanize on all body parts.

 

[felixc]

So is it preferable to stay away from aluminum cars for another several years, until they find ways to slow down the corrosion?

 

[TVP]

The corrosion performance of automotive aluminum alloys (castings using alloys such as 319, 356, & 380 and formed/forged parts using 6061) is considered acceptable for the expected lifetime of current automobiles-- 10 years or ~ 250,000 kilometers. Keep in mind that most aluminum components are not coated or plated, unlike iron and steel components.

Another consideration is galvanic corrosion. Historically, many applications have involved aluminum components being directly fastened to iron/steel components, thus resulting in galvanic couples. Steel fasteners with only zinc plating used to join these components also results in a galvanic couple. Newer vehicles have improved somewhat by using better design techniques (Al-Al joints, drain holes, etc.), better coatings (Al- & Zn-filled organics), and better alloys (minimum Fe, Ni, Zn content in Al castings). Continuous improvement will see enhanced corrosion protection from better pre-treatments and coatings, use of aluminum fasteners (rivets, screws, nuts, etc.), and fewer questionable joints.

 

[RRahul]

Most of these corrosion that you see happening is because of the Chloride ions present in the de-icing salts. Since, Chloride ions attack Aluminum very easily you might be seeing corrosion chiefly of the intergranular type. Modifications like altering the grain size and shape, introducing elements like Ti and Zr in the grain structure to achieve Long Life capability are some measures that the industry is working on. So, dont run away from Aluminum .....we might have a solution soon.

 

[rossibeeter]

Hello

As the manager for the vehicle corrosion testing department for a major European vehicle manufacturer this is a question that is on everyones mind at present. Firstly - Aluminium is the future direction of many auto manufactures world wide - this is mainly because of the large advantages it has over steel (weight, improved corrosion resistance etc)
The problem you refer to with the Ford branded vehicles is a company issue - To build a vehicle with Aluminium does cost money because you must protect from galvanic corrosion etc etc and Ford inherently deliver product at minimum cost to the business. BMW, VW and Volvo in particular for example have been using Aluminium on autos for over 15 years - and you do not see many corrosion issues with those. To answer some of the statements above - Just because the component is underbody and exposed to de-icing salts is not a major reason for the issue - Our testing has shown that as long as the localised pH does not exceed 10.5 then the self-passivation effects of natural aluminium is enough to make it last.
The only real problem we have to address now is the cosmetic side of it. If aluminium is not treated then it will 'fur' under the influence of salts - This however will not be a problem if the material is painted
Hope this helps