Rod MI about the AL wheels...

The best I have found so far is a product that can be found in any industrial/commercial electrical supply house. The particular one I have now is branded under the "Hubbell" name. Full designation is "Hubbell Power Systems Versa-Seal VS-8B electrical joint compound". This is listed for use on electrical joints of Al-Al, Al-Cu, and Cu-Cu. It is basically an electrically conductive compound that also functions as a water repellent, anti-sieze and anti-corrosion compound.

I have used this between wheels and drums, Al tools boxes and steel frames, ect. The surfaces must be completely clean and free of any previous corrosion, oil, dirt, ect. Apply a thin layer to both sides of the joint and assemble. This product is yellow in color. There is another common one with similar properties called Noallux or something to that effect sold under the Ideal brand name. This is gray in color and has a much lighter body to it. It does not work as well as the Hubbell brand one as it is more prone to run out and drip off especially when temps get above 80F. The Hubbell does maintain well even on semi-truck wheel applications.

Petroleum oils and greases are normally non-conductive of electric current and can actually cause more corrosion between dissimilar metals such as Al-Fe joints. It also works well if used on ground wire/cable connections to the frame and or engine block. Works equally well on battery terminals but you must use a very very light coating to prevent any run-off, it is conductive and if contact is made between battery terminals or positive and vehicle frame, the battery will short out and drain. Do not use it on light connectors or such because it will also short them out. Another good place to use this product is when you install Aluminum or stainless steel fasteners through or into any Fe alloy.

For light plugs/lamp holders, you can get a special electrical grease at most auto parts stores that is non-conductive and will not hurt the rubber/plastic light housings and or wire insulation. This is usually a light brown (dark beer color) and semi-transparent.

BTW, some people will tell you that placing a piece of rubber between steel and Al will stop the corrosion... tried it, don't work either. Even using this compound, you will still get some corrosion but it has been the longest lasting and most effective thing I have found to limit it.

Steel wheels can split around the lug holes from over tightening just like Al ones can. Most steel wheels have one or more weld joints that can also crack however it is rare. Both have corosion problems but steel is usually the worst for bead corrosion. Al wheels can get bead corrosion but it is less likely than with steel. Most bead corrosion problems on any wheels are caused by tires that do not conform properly to the wheel itself and allow water, salt, ect to get between the tire and rim.

Al wheels subjected to rough roads and off road use will usually have a higher failure rate than steel wheels subjected to the same type of abuse. The type of alloy used in the wheel is also a major concern as to the application of the wheel. The fancy type wheels used on SUV's and such are not actually designed for anything much more than looks and open smooth highway running. The Al wheels used on semi-trucks and trailers are quite different animals. These usually have a heavy duty construction that is designed to take the constant pounding of heavy loads and not so smooth roads. They do however have a limit to what they will take. Using these in such applications as mining and other off-road and corrosive duty is not acceptable. These environments are hard enough on steel wheels and seriously reduce the life span of the wheel itself. Fancy wheels are generally made from harder alloys so they can be made thinner and lighter. With Al this is a trade off between long life and durability. The harder the alloy, the more prone it is to sustain stress cracks and the softer the alloy, the more vibration and impact it will absorb without stress damage. A soft alloy will give and flex while a hard alloy will not, it'll crack first. The same story held true for dump bodies being made some years ago pushing the use of a steel alloy known as "T-1". It did not wear or dent as did the standard A-36 alloy but in a short time they were reduced to scrap because of stress cracks. Every box I have seen made from T-1 looked like an egg shell that was stepped on while the plain old A-36 steel bodies were dented up and worn down but still in relatively good shape. Same with Al dump bodies. Those that were welded with 5356 alloy wire usually suffer a high number of failed welds while those welded with the softer 4043 alloy wire did not. All the repairs I do on Al bodies are done with the 4043 and those areas prone to abrasion wear are capped with 5356 that does not touch both sides of the weldment at the same time, if it does, a crack will start and run the weld seam.

Those Al rims used on motor homes and medium duty trucks are usually much lighter duty than those used on semi-trucks. These are used primarily to look good and a small secondary fuction is to reduce weight. These rims can last a good number of years but they must have proper installation and upkeep to maintain their structural integrity.

Another problem is expansion and contraction. As wheels heat up from running and using brakes, they expand. They more they expand, the more dirt and crud that is allowed to enter into areas such as around the bead and also into the grain of the alloy itself. Expansion also increases the pressure between the lugs and the rim. The Al wheel expands much faster than the steel or cast iron brake drums and hubs. This constant movement between the rim and hub also causes stress to be induced into the wheel. The better the heat transfer from wheel to hub, the less expansion differential is seen between the dissimilar metals. Adding the anti-corrosion compound does help transfer heat better between the wheel and hub, while it is not a perfect medium, it does help more than nothing. Corrosion acts as a heat insulator and causes more problems than just the loss of structural integrity.