Coating on Bolts - Aluminum Differential Carrier
01-11-2003, 10:24 PM
#1
Melting Slicks
Thread Starter
Coating on Bolts - Aluminum Differential Carrier
On my 1980, the strut bracket attaching bolts run through the aluminum differential carrier. They appear to have a blue coating on the shaft of the bolt. I presume this is for corrosion control. I don't find reference to any coating on these bolts in the A.I.M or the shop manual. The bolts attaching the spare tire hanger to the differential carrier also have this coating.
Does anyone know what this coating is?
Does anyone know what this coating is?
01-12-2003, 02:10 AM
#2
Re: Coating on Bolts - Aluminum Differential Carrier (mapman)
Sir,
The AIM does not show a part number reference for the coating because these bolts were coated long before they reached the St Louie or BG assembly plants. Although some hardware may receive incidental paint over spray during assembly plant use - the finish or plating or coating or special treatment or heat treating are usually set during the fasteners manufacture at a subcontractor.
McLellans recent book: “CORVETTE from the INSIDE” has a section on the engineering and development of these coated fasteners to help prevent and essentially only slow down electrolytic damage when assembling Aluminum parts to/and or with Ferrous parts. As Aluminum became more prominent, their concern was great with suspension, brake and steering parts being the sacrificial party in this destructive process. If I remember correctly, the potential failure of these Aluminum parts exposed to rain and road salt was paramount due to their safety concerns.
Scientifically, the Aluminum parts were more susceptible to this problem due to their position in the Electromotive Force Series. If I remember correctly, this series list different elements and their tendency to loose electrons in a chemical reaction. Those that loose them faster and easier are the ones that get “eaten” away faster when they “meet” or are in proximity to those that don’t loose them as easily – but that the actual chemical reason why at the atomic level. Who really cares? :D.
If you local speed shop does not know a source, email McLellan and he may know the trade name for that coating. Or call a Loctite help line as they do more than just make “glue” for bolts.
Geoffrey Coenen
NCRS #2473
NCM Lifetime #105
Precision Valley Corvette Museum Charter Member #20 (I think)
Vettehead #18-1
Retired #1 56, 63, 67, 68, 68, 69, 75, 99 and I want more! :D :leaving: :leaving:
The AIM does not show a part number reference for the coating because these bolts were coated long before they reached the St Louie or BG assembly plants. Although some hardware may receive incidental paint over spray during assembly plant use - the finish or plating or coating or special treatment or heat treating are usually set during the fasteners manufacture at a subcontractor.
McLellans recent book: “CORVETTE from the INSIDE” has a section on the engineering and development of these coated fasteners to help prevent and essentially only slow down electrolytic damage when assembling Aluminum parts to/and or with Ferrous parts. As Aluminum became more prominent, their concern was great with suspension, brake and steering parts being the sacrificial party in this destructive process. If I remember correctly, the potential failure of these Aluminum parts exposed to rain and road salt was paramount due to their safety concerns.
Scientifically, the Aluminum parts were more susceptible to this problem due to their position in the Electromotive Force Series. If I remember correctly, this series list different elements and their tendency to loose electrons in a chemical reaction. Those that loose them faster and easier are the ones that get “eaten” away faster when they “meet” or are in proximity to those that don’t loose them as easily – but that the actual chemical reason why at the atomic level. Who really cares? :D.
If you local speed shop does not know a source, email McLellan and he may know the trade name for that coating. Or call a Loctite help line as they do more than just make “glue” for bolts.
Geoffrey Coenen
NCRS #2473
NCM Lifetime #105
Precision Valley Corvette Museum Charter Member #20 (I think)
Vettehead #18-1
Retired #1 56, 63, 67, 68, 68, 69, 75, 99 and I want more! :D :leaving: :leaving:
01-12-2003, 04:01 PM
#4
Race Director
Re: Coating on Bolts - Aluminum Differential Carrier (mapman)
I saw exactly what you're describing when I dropped my spare tub on my '80 down last year. Myself, I think it's some sort of "locktite" material for the nut on the end of the bolt that goes through the "J" hook.
