I am attempting to clean/polish my exhaust but I am now stuck and unsure what to do next? Started off with this: Got to this after three rounds of cleaning with Dr.Downpipe exhaust cleaner which pretty much got all the rust off: After more than an hour of polishing by hand with some green abrasive pad I nicked from the kitchen and some rags: I cannot justify 50+ hours of polishing by hand to get the whole exhaust to be as shiny as the 50p size piece I have gotten so far, any suggestions of how to get there quicker?
get it bead blasted to get rid of all of the heavy corrosion and then get a Dronco polishing kit for a grinder and go at it with that https://www.weldequip.com/polishing-set-115mm.htm or... get it blasted and Cerakoted in a colour of your choice then never need to worry about polishing again - having polished multiple exhausts before I took this route with my 1098 and i couldn't be happier
then run a mile. harpic is hydrochloric acid based which is not compatible with 300 series stainless steels
The very reason I didn’t go down this route, looked up the harpic idea on YouTube and found a video from someone describing the damage it actually does to the metal.
What worked for me was various grades of emery cloth cut into strips and wrapped around the pipes to polish all the way round the tubes. Starting with a coarse grit really cuts through the corrosion and staining leaving a brushed finish which you can improve with finer grades. Using a drill with a brass wire brush gets into the corners and angles. I also used the rubber blocks embedded with abrasives which are really useful for corners and flat surfaces. If you want to get a more polished finish complete with Autosol and rags wrapped around the pipes. The abrasives really speed up the process and you can choose how far you want to go and what type of finish you want to achieve. I was quite happy with the result on mine without spending days on it.
My response was a suggestion that people check what's been tried/recommended, not a specific recommendation to use Harpic. However, I'm interested now. Yes, I agree that 304/316 is not suited to a hydrochloric acid environment but surely if that acid were to be used to remove a microscopic film of that material (and/or its existing corrosion) then thoroughly washed off, is there a residual problem? This is not a challenge, merely interest.
agree, in safe hands/controlled environment nothing wrong with a bit of etching if corrosion is bad enough, as long as you can halt, or do your best to halt the process when "done". As most on here know, phosphoric acid, which most of us have consumed in Coca Cola at some point, is sometimes the easiest solution (npi) when dealing with severe mild steel corrosion, but it does tend to keep going if surface is craggy enough, and of course as soon as you wash it, it will "go brown" almost immediately.
It doesn't just remove a little bit of the metal in the way abrading the corrosion off with media blasting or sanding etc would. The HCL reacts with the protective chromium oxide layer on the steel and dissolves the chromium leaving it chromium depleted, removing/reducing it's 'stainless' property, more likely to general corrosion, SCC etc, especially around the welds where the HAZ is probably already chromium depleted I know it's 'just' a bit of exhaust pipe, not the stuff I deal with at work, but I still just wouldn't bother.. in the same way I wouldn't recommend washing your kids with bleach
re: "etching" - post was a generalisation, it's often the last resort for me but still more than happy to continue using this route in the future if need be.
You could try pickling paste which is suitable for ss304/316. It is sulphuric acid based so needs to be treated accordingly It does a very good job. It will also pasivate the surface helping resist further oxidation
