Indi
Member
In the manual it says the green coating on lots of the original fasteners is Dachromet, a corrosion preventive coating used to prevent contact (Galvanic?) corrosion.
Possibly this coating wearing off is the reason many of the 10.9 high tension bolts are said by the manual to be once use, even though they are not stretch bolts and are structurally ok to reuse. This would mean that by reusing the old fasteners, the female aluminum threads would be gradually weakened, as the electrons transfer to the more noble ferrous bolts, as well as increasing the risk of the fastener seizing in...
Even if this is the case there is not much to do with the information as none of the genuine VWAG replacement bolts seem to come with this green coating on, even though the part number matches the original.
I've been using Aluminium grease to reassemble everything so hopefully the combination of the grease sealing to keep water or any other electrolyte out of the threads, and a little bit of extra sacrificial aluminium is enough to prevent any damage.
Just thought it was interesting and wanted to share, I don't know if this is the case or not but seemed like a potential explanation.
Possibly this coating wearing off is the reason many of the 10.9 high tension bolts are said by the manual to be once use, even though they are not stretch bolts and are structurally ok to reuse. This would mean that by reusing the old fasteners, the female aluminum threads would be gradually weakened, as the electrons transfer to the more noble ferrous bolts, as well as increasing the risk of the fastener seizing in...
Even if this is the case there is not much to do with the information as none of the genuine VWAG replacement bolts seem to come with this green coating on, even though the part number matches the original.
I've been using Aluminium grease to reassemble everything so hopefully the combination of the grease sealing to keep water or any other electrolyte out of the threads, and a little bit of extra sacrificial aluminium is enough to prevent any damage.
Just thought it was interesting and wanted to share, I don't know if this is the case or not but seemed like a potential explanation.