Mercedes lug bolt restoration

I have recently purchased a set of 15×7 AMG ‘Penta’ wheels for my 1977 450SLC.   These wheels did not come with lug bolts, but I had a set from when I had the replica Fuchs alloys on the car.   The other day I got those bolts out to check them for when I install the wheels on the car.

The bolts were in pretty good condition overall, but suffering from surface rust, particularly on the heads.  That wouldn’t look very good with the new nice wheels.  Instead of buying new bolts, I decided to see if I could perform some lug bolt restoration.

My first try was using the Autosol Metal life saver.    The first picture shows the bolts pre-restoration.

The Metal life saver did a good job on the bolts that only had light corrosion, but not such a great job on the worst of the bolts.   It also took quite a long time doing each bolt.   The photo below shows the results of about 90 minutes of work on the bolts.   An improvement, but enough to use with the nice new wheels.

I figured as the Autosol product had been working reasonably well, it might make sense to soak the bolts in that solution.

After about 48 hours, I could see a noticable improvement, so I added more autosol to submerge the bolts and left them for a few more days. After about a week of total time in the solution, I was able to clean the bolts with a rag and an old toothbrush. They came out great.

the final product looked really good.   These bolts would look great and not spoil the look of the nice new wheels.   I figured job done – I was wrong.

A week later I went back to take the bolts down to where wheels for when I mount them.   I was in for a nasty surprise.   All the bolts were really rusty again – worse than when I started.   I surmised that the bolts must have come with some kind of rust resistant coating.   This degrades over time, allowing the rust to start, and explains why some bolts were worse than others.   Soaking the bolts on the autosol solution not only ate away the rust, but the remainder of that coating.   I should note that nowhere on the Autosol bottle does it suggest to soak metal in their product for days.

My thinking was that I needed some way of adding a coating that would stop the rust from starting.    I didn’t want to paint the bolt heads silver, as I thought they would clash with the colour of the actual wheels – even if very close.

I finally settled on trying to paint the bolt heads with some clear coat.   This should stop them from rusting, but also mean I have to be quite careful when tightening them.    The clear coat probably would not survive a mechanics rattle gun, so its going to be a short to medium length solution – if it works.   I started by soaking and cleaning the bolts in Autosol – again!

The next stage of my lug bolt restoration was applying the clear coat.   I used cardboard to ensure that the clear coat did not get on the threads.

Per the directions on the rattle can, I did a few lighter coats on the bolts.  The glossy clear coat made the bolts look like they are wet.   I don’t think this will be too much of a problem.    The picture below shows the results after applying the final coat.   Note that there is not white residue on the bolts, that is reflection.

Overall I think they came out pretty well.   I won’t really know until I have the wheels mounted for a couple of weeks to see if rust will form.   In order to protect the threads, I have applied a small amount of copper grease.   Normally I would do this when installing the bolts, but I have done it now to help protect them.

I won’t be using these bolts for a couple of weeks.   The car is going in to have the front subframe mounts done, so I won’t mount the new wheels until after that.

If I was doing another lug bolt restoration I am not sure if I would do it this way again.   I may try soaking them in a less potent cleaner to preserve the original coating.    Having said that, the coating was already compromised where the rust had formed, so I am not sure what difference it would made.