Forum Chat #60 – Is it worth treating a corroded rear sub-frame??

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Welcome to BamfordRose and its forum chat time. This week I’ve picked up on a couple of pictures and a description of a rear subframe restoration on a V12 Vantage this particular car is a customer of ours, although the detailing work that he’s had done and the subframe treatment was not done here. This car is absolutely mint and was not really worthy of subframe restoration at this point. The corrosion, the degradation was not that severe.

So, there’s two points in this video that I wanted to pick up on. One was the actual point when it came to needing to restore the rear subframe and the other was to question whether it was worth treating it during that interim period prior to taking the subframe out and shot blasting and powder coating and doing a proper restoration. So, the front subframe is aluminium structure. The rear subframe is tubular steel. From original production, there is only a wafer-thin coating, so corrosion unfortunately does creep in quite quickly, quite soon.

Now if we have a look at a typical subframe and I’ve circled the section in green, we can see what normal corrosion looks like. You know, this is just surface corrosion, which if you’ve got a wire brush on would remove and you’d be left with very healthy, almost perfect, bare metal. And none of the wishbone arm, suspension mounting point, brackets are compromised, not weakened and it wouldn’t be failing MOT.

In this next picture, we can see that whilst it was with the detailers, they’ve done a treatment on the subframe. Now if you zoom in on areas in that picture, you can see that there’s still some degradation from the corrosion which the treatment has gone over the top.

If we now look at a picture where we can see the wishbone arm going into the brackets on the subframe, this is actually one treated a year ago. So, you can already see that in the space of a year that the treatment is flaking off and the corrosion is still present. This is because the correct course of action is to completely shock the entire component and then corrosion inhibit and powder coat.

So, here you can see in these two pictures, this is a subframe which we’ve done just that. And the finish is better than what it was from original factory production and is going to last considerably longer before needing attention again.

If you were to look at your car underneath on a ramp and go back to the picture where I circle here in green, typical surface corrosion, you might look at that and be quite horrified that your Aston looks like that. And then if we go to the picture where the detailers have treated the subframe, it might give you a cozy warm feeling that underneath your car now looks more respectable. Unfortunately, that really isn’t doing anything for the longevity of the component and isn’t really going to alter when the subframe needs removing and shot blasting and powder coating, which means it’s pretty pointless to do the subframe treatment. Not least, because you’re not going to be able to treat areas which are just inaccessible.

So, in my opinion, it’s pretty pointless to invest in any treatment works like that and year on year when you have your annual service inspection, you’re better just to work with a garage and each year note down that there’s perhaps some surface corrosion. You know, it looks a bit gritty but there’s no structural safety concerns. It’s not going to fail.. Then you’ll probably get to a point, I don’t know a few years into the future, and maybe the garage is saying at their inspection report that the corrosion now is quite significant. And even then, you’re not going to fail an MOT. The corrosion has progressed to a level which just by looking around those safety critical structural areas is just a little bit too much, a little bit too progressed. And then it’s the time to remove the subframe, shot blast, powder coat and perhaps combine that with rejuvenation of the roll bar and a few other brackets maybe powder coat all the road springs as well, just so that the whole underside looks like it’s been refreshed.

There are too many variables of storage and other environmental circumstances to pinpoint exactly when a subframe will need restoration. There’s some 10-year-old subframes out there at the moment that do need restoration and there are some 15-year-old subframes on the original DB9 that are fine. Inevitably, the corrective action is going to be a full removal, shot blast and powder coat. And that activity at the future point in time when you decide to do that is going to be no different than if you had treated in that interim period the subframe with some inhibitor, meaning that ultimately there’s absolutely no benefit of investing any time or money into that interim corrective procedure. It’s not going to change when the subframe needs a full resto, all it’s going to do is give you a cozy warm feeling but the subframe looks nice and black colored instead of displaying a little bit of surface corrosion.

Hope you like that forum chat and as ever really helps us if you can like, comment, and subscribe, and we’ll see you in the next forum chat.

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