Rear Subframe Surface Rust Descaling in an Aston Martin DB9

Some of you may have seen one of my (@aston2209) previous Blog on changing the rear lower wishbone assembly and at the time I commented on the condition of the rear subframe. It had quite a lot of flaky surface rust that was both unsightly and could lead to more aggressive corrosion in later life for Aston 2209. At the time I wanted to undertake cleaning up the subframe but since it was in the winter and there was a lot of damp atmosphere from day to day, I decided to leave it until the summer. However here we are in May and we have just gone through a really long period of dry weather with warm temperatures and seeing as we are also in “lockdown” due to the Coronavirus it seemed like a good time to do the job.

[Editors Note:  I’d like to thank Mike Potts (@aston2209) for contributing his time and knowledge in writing this article – Thanks Mike!]

I didn’t have an air operated needle de-scaler so turned to eBay to see what I could find. I have seen many large industrial de-scalers in action in steelwork fabricators and on construction sites during my career as an engineer but I was looking for something more compact that I could use to get into the more confined spaces of the subframe.

This is what I found and maybe electrical versions of the unit are available for those of you who might not have compressed air on tap.

Air operated tools are always very noisy so you will need suitable ear defenders and as we are going to be loosening rust you will need good goggles.

The winter brings snow and ice and the Local Council spreads salt on the roads to get rid of the ice to keep people safe. Unfortunately, there is a price to pay in terms of the effects on the underside of our cars. Prolonged exposure to the salt and general wet conditions of winter start the corrosion process that in years gone by used to see cars become rust boxes in just a few years. Better quality steels, modern treatment techniques and better chassis design now means that cars don’t rust anything like they used to through the 60s and 70s. That said once your car is over ten years old, I believe it’s time to start inspecting the underside for the start of any corrosion and like anything catching it early is the key. As you will see this is what we are up against.

Rear roll bar mounting before descaling

Aston 2209 is 15 years old so is well into the time where it is necessary to check and treat any offending corrosion. It’s not difficult to keep on top of the corrosion as long as you are prepared to put the time in to descaling and painting. Due to the amount of parts both attached to the rear subframe and the openness of the subframe structure spray painting is not an option. Also, as the subframe is in place you cannot access the top of the subframe but by using a mirror I could see that fortunately there was little if any corrosion in areas that would be difficult to get at with a small paint brush.

After descaling

After using the de-scaler you get a good rust-free surface but this still needs to be worked on further to get rid of any remaining fine rust colouration and to get a good surface for the paint to key to. After wire brush polishing you can get a surface finish as here that is ready for the paint to be applied.    

After wire brush polishing
After wire brush polishing

I used smooth finish (it also comes in a hammered finish) black Hammerite paint that I’m sure is well known to all but for those who don’t know of it, this is what they say on their website:

Smooth Black Hammerite (https://www.hammerite.co.uk) Direct to Rust metal paint, comes in various colours and tin sizes. Providing up to 8 years protection from the elements, it can be painted straight onto any metal or rusted surface without the need for primer. This tough paint is simple to use and comes with on pack full preparation, usage and cleaning instructions. Perfect for sealing those rust prone areas of bodywork.

When you use the paint you cannot clean your brushes in ordinary terps or white spirit you need to buy the thinners/solvent which cost about the same as the paint itself, or you do like I did and buy some cheap brushes off ebay and bin them afterwards.

The finish painted subframe is pictured below and I will be checking it on a regular basis probably once a month to give any additional feed-back through the Blog if necessary. If you hear nothing then there is no problem !!!

Finish Painted
Finish Painted

Video

Check out this video of the process.

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