I want to clean a driveway that's in good shape but looks bad because of the oil and rust stains on it. The stains are a couple of years old and have really set in. Could anyone help out with some good ideas of what to use to clean it?
I cleaned a badly stained driveway a couple of years ago with my Power Washer and a special cleaner made especially for driveways and it worked great. Unfortunately, I can't seem to find that special cleaner anymore.
I've found one guy on the web that says to use muriatic acid, but the driveway belongs to my uncle, and I wouldn't feel comfortable using something that might permanently damage his driveway.
You don't need the acid, it will not do a good job for your problem and could make the problem worse next time. Stop at the home improvement store and they will have several cleaners for concrete. Most work well for what you have. Follow the instructions and follow up with the power wash using it as a final rinse.
I never heard that pressure washing a concrete driveway can damage it, unless it is already breaking up or spaulding. But the acid, even when diluted, will react with carbonate compounds in the concrete. Keeping muriatic acid around the garage, basement or whatever will quickly corrode metal parts in the area, and disposing of it properly and safely becomes a problem.
There are a "few guys on the web" that think muriatic is good for cleaning anything and everything. It is great for etching concrete, but pretty nasty as a "cleaner". It won't get through oily/paint film, so it will eat around it. Diluted 10%, as label calls for, still gives a strength that creates clouds of fumes and makes a bit of noise as it reacts. With my limited experience, I would not use it as a cleaner. It eats away concrete and exposes more aggregate, possible weakening the surface as far as water freeze/thaw cycles go. The dark spots from hamburger grease or careless work remain after the acid, making very little difference in the appearance. Cat litter is another "remedy" but leaves a residue that is at least temporary. Pressure washing can do damage, like the acid, if blasted with too much pressure.
Not having access (without renting a pressure unit) I did what a swimming pool tech told me once. I've used this process for over 12 years and it looks great.
Pre-treat the rust stains with CLR - realize you're going to use a complete bottle or more so be prepared. Put one pound of pool shock (available at local bldg supply, Wal Mart, etc.) in a 5 gallon bucket. Pour in one gallon of boiling water and add the pool shock (strong chlorine). Add two gallons of cheap laundry bleach. Stir with a scrub brush on a long handle. On a hot summer day - (and being careful not to splash it on anything you don't want bleached or skin burned) lightly brush it onto the concrete. Allow it to dry - do not hose it off. By the end of a sun shiny day - you'll be amazed at the results. All the black marks from rain and washoff will be gone. I did my driveway and sidewalk that way and the neighbors actually complained that theirs looked like hell because mine looked like it was freshly poured. It's easy to do - involved very little labor, no scrubbing, and the results are great. Use caution when breathing the fumes - (read labels ,etc.) It's the same stuff they use when they close the pools on Mondays to treat for algae, fungus, etc. The odor dissapates with 24 hours and it doesn't destroy the integrity of the concrete. It kills the grass in the expansion joints as well - so be sure not to splash it over on the lawn, plants, etc.
Muriatic acid won't cut grease, you need a soap, or possibly a solvent. Your local hardware/home store will have grease cutting cleaners suitable for driveways and pressure washers, stop and ask.
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