[Shop-talk] pressure washing driveway

[Lee Daniels]

Most methods for removing rust stains involve some kind of acid, from vinegar
(relatively weak) through oxalic acid (moderate) to muriatic (hydrochloric) -
strong! (don't go there). The trade-off is that concrete also dissolves in
acids, so choose your poison carefully.

Here's a list of nearly all the tricks I've ever heard, all in one place:
 https://www.wikihow.com/Remove-Rust-from-Cement
Note that this one also mentions trying Trisodium Phosphate (TSP) - which is
strongly basic, opposite of acidic, not sure if that's going to help. TSP is
great for oils and greases though.

I'm fond of oxalic acid - a good source of it is Bar Keepers Friend. Rust
(iron oxide, Fe2O3) does not dissolve quickly, so put on your vinegar/whatever
and let it sit for a while, maybe brush it in, then rinse and brush more.

I don't envy you!
 Lee



On Tue, June 26, 2018 21:03, john niolon wrote:
> needing to pressure wash my driveway...  did a walkway today 3' wide and
> 50' long... 4 hours.  That is with water only no chemicals or soap... now
> the driveway  100' long and 15' wide with a 50' x 25' area between
> house and shop... usual stains, lots of oak trees... drive is black with what
> I figure is mold or oak tree crap...
>
> The concrete area in front of my shop is pretty badly stained from grinding
> and welding and not cleaning up properly. Lots of iron rust stain that has
> been there a long time. Is there anything that will work to remove, etch,
> etc. these stains so when I pressure wash the drive I don't have this
> discolored area ??? Don't have pets to worry about but do have nice grass on
> either side of driveway so rinse off might be a problem for the grass.  I
> have a 3000psi 4gph Dewalt washer so plenty of power.
>
> looking for recommendations on detergents, cleaners, etc... also on technique
> other than just bear down and get it out...  I'm old (70) so make it easy
> on me !!
>
> thanks John