Exhaust Rust Clean-Up And Prevention Jul 6, 2015 11:37:36 GMT -5 katastroff, dmartin95, and 1 more like this
Post by 90GTVert on Jul 6, 2015 11:37:36 GMT -5
Here is a recent pipe I built,1st pic is as welded with scale and blued metal;
This is after acid wash several times;
The acid is phosphoric acid.
It is probably the ultimate rust renovator.
The difference between phosphoric acid, and other acids, is that it actually converts the rust to something else completely (it's on the web if you google it).
The rust becomes a hard black shell, that can then be painted over.
In effect, it creates an additional barrier to rust, underneath the paint.
It is a must have acid for any workshop dealing with older kit.
Buy it at 75%, and mix it no more than 1 part acid to 1 part water........ diluting it to 30% is probably ideal.
Buy 1 litre and it will last you a lifetime, as hardly any of it is used.
Mix up a tiny amount into a container, each time you use it........ it's as thin as water, so it just spreads.
With a brush, spread a coating over the rust, and let it be absorbed.
Spread a second coat after it has dried off...... it should be enough...... but a third will definitely do it
You'll be left with a beautiful black item (if you like that sort of thing)
Note: if you mix it too strong, it will simply etch away the rust, defeating the object..... unless that's what you want it to do.
Be very careful with this stuff, and were goggles, against brush spray.
Phosphoric acid acts as a rust converter by changing brown rust (iron oxide) into black ferric phosphate. This black coating can be scrubbed away leaving a new metal surface beneath or it can be left in place in which case it acts as a protection against further erosion.
If you don't want a clear protective coat, barbeque paints are a popular choice for exhausts. The exhaust below is painted with Rustoleum's black BBQ spray paint.