How to deal with oil stains on concrete

How to deal with oil stains on concrete

So, you have some oil stains on your concrete…

One of the most popular questions that we are asked at Phase III is, “How do I clean oil stains on my driveway?”.  My typical response is, “Did you fix what was leaking on your driveway?”, because it is no use cleaning your driveway, if something is going to continue leaking oil on it.  To get a better understanding of how to clean the stain, we need to understand what the stain really is.  Motor oils are derived from petroleum-based and non-petroleum synthesized chemical compounds. Motor oils today are mainly blended by using base oils composed of hydrocarbons (mineral, polyalphaolefins (PAO), poly internal olefins (PIO), thus organic compounds consisting entirely of carbon and hydrogen.  Now that we cleared that up, 99% of the time, a spill on your driveway came from used oil that has dripped from a cars engine, transmission or differential.

Octane molecule C8H18 contains 8-carbon molecules and 18-hydrogen molecules

The majority of hydrocarbons that are found naturally occur in crude oil, where decomposed organic matter provides an abundance of carbon and hydrogen which, when bonded, can catenate (to form a long chain structure) into seemingly limitless formulation of oil, gas, grease, gasoline, diesel fuel, etc.  The primary ingredients found in crude oil are; Carbon 83-87%, Hydrogen 10-14%, Nitrogen 0.1-2%, Oxygen 0.1-1.5%, Sulfur 0.5-6% and metals which typically are less than 1000ppm.  Used motor oil turns darker as the lubricity additives and gas molecules break down from heat, leaving a higher concentration of carbon (that’s why it is darker than new oil).

With that said, you noticed that carbon is the main ingredient in oil; it’s what makes crude oil so black.  You also noticed that there are several gases involved as well as other organic materials like metals which are the result of trace minerals that exist in soil like iron, copper, zinc, but these percentages are very low compared to carbon.  When we have an oil stain on a surface like concrete (which contains millions of very small pores for the oil to get trapped in) the oil penetrates into and under the surface until it is extracted out.  Many people use absorbents like Oil Sponge which has a unique “wicking” capability that draws the oil to the surface, helping to reduce staining and collateral environmental impact.  Many shop applications use a mop and bucket system immediately and again, this helps to reduce staining and collateral environmental impact.

Then there are the ones that choose to respond to the spill several days, weeks or months later.  When this happens, that oil sits in the pours and begins to oxidize.  Oxidation occurs when an addition oxygen molecule is added to the hydrocarbon molecule.  With one extra oxygen molecule, the hydrogen (gas), nitrogen (gas) and additional oxygen molecule (gas) are released into the atmosphere… essentially evaporation is occurring.  As the oil is oxidized, more and more carbon is left behind which is organic just like the concrete, but now the concentration level is closer to 90-95% and it’s very dark now.  When you use a cleaner like Oil Sponge UC+ or Oil Sponge HD for concrete cleaning you are breaking down the residual oil that hasn’t oxidize completely.  If you use the right dilution ratio (yes, you need to dilute and rinse with water for efficacy) you will effectively clean the hydrocarbons (carbon + hydrogen + nitrogen + oxygen + sulfur + oil additives + sludge + dirt) from the surface.

But you still have a stain, right? The remaining stain is more of a combination of residual oil under the surface and staining from the high levels of carbon left behind from oxidation.  Carbon is an excellent dye.  Did you know that tires are naturally white?  Carbon is used to dye them black.  Coal is composed primarily of carbon along with variable quantities of other elements, mainly sulfur, hydrogen, oxygen and nitrogen (sound familiar?).  Charcoal is primarily carbon, burnt wood turns black as the only thing that remains from the cellulose and lignin is the carbon.  All of these items are dry to the touch, but leave behind a black stain, the same stain that remains in concrete after you’ve cleaned it up.  So, is the surface really free of oils?  Is the surface slip free?  When you touch it do you get oil on your fingers?  Proper use of Oil Sponge branded cleaners should have removed as much oil as it came in contact with (remember there are millions of pores in concrete).  Repeated use and a good housekeeping protocol will help to clean any remaining sub surface oils and the stain will lighten with time, but it may never truly go away.

There are other ways to remove concrete staining, but these are either very caustic or acidic solutions, which in turn damage the concrete.  These quick and dirty methods will cost you more in the long run as you will have to eventually replace the concrete or resurface it.  The best method is to clean the spill up when it occurs.  If your stain is old and dry to the touch, you will need to be patient as it will take a long time to remove, but it can be done.

Here’s a clever way of using Oil Sponge to absorb a fresh oil spill on concrete surface

After the spill has occurred and as soon as possible afterwords, you need to respond with UC+ and either Oil Sponge AB or AB+.  There is some really cool science behind this technique, which is called a “poultice”.

As defined by Wikipedia, a poultice (poul·tice, noun), is a soft, moist mass of material, typically of plant material or flour, applied to the body to relieve soreness and inflammation and kept in place with a cloth.
Steps 1-4 should be done after you have initially cleaned/recovered the spill.
Step 1:  Use just enough of our Oil Sponge UC+ liquid cleaner (un-diluted) to cover just the spill with a thin layer and let it soak-in to the concrete.
Step 2:  Cover the spill area with either Oil Sponge AB or AB+ absorbent.  Make sure the absorbent is about 1/4 inch thick and leave in place for at least 3 hours, usually 12 hours is optimal.
Step 3:  Using a shovel or putty knife, scrape the poultice (absorbent material) from the concrete surface and dispose of it properly.
Step 4:  Rinse the concrete with clean water while agitating it with a stiff bristled brush.
This technique works very well, but many spills will require multiple treatments.  Always let the concrete completely dry before retreating.
The reason that this method is very successful is because of the ability of Oil Sponge to wick oil vertically.  Many absorbents will only absorb what they physically come in contact with, but will not continue to draw the oil further into the absorbent material.  Oil Sponge works like the cotton wick on an oil lamp.  Have you ever wondered why that wick never burns completely away?  The reason is, when the wick is introduced into the oil, the wick draws the oil vertically until it reaches the top of the wick.  When the wick is lit, it is not the wick that is actually burning, but the “volatile” oil vapors coming off of the top of the wick.
So, in our “poultice” method, the Oil Sponge absorbent is acting like a wick, to draw the oil vertically out of the concrete.  But why do you need to use the Oil Sponge UC+ product?  Because of the many “micro-pores” that exist in the concrete for the oil to hide in, we use the Oil Sponge UC+ as a connective fluid to attach the oil to the absorbent.  Since the Oil Sponge UC+ (un-diluted) has a viscosity similar to oil it connects well with the oil.  Also, the UC+ helps to break the oil droplets into even smaller droplets, so they are easier to draw out of the concrete.  The residual Oil Sponge UC+ that is left in the concrete after removing the poultice will aid in the washing residual oil out of the concrete in the final step.
Remember, this procedure will only work with fresh spill which are 1-2 days old.  If the oil spill is old and dry, it will not work properly.\

General Floor Cleaning Protocol

Always clean-up your spills as soon as they are noticed.  This will prevent “slip-and-fall” injuries, unwanted tracking and more spills to take care of.  When trying to remove oil compounds and oily soils from concrete, there needs to be the understanding of how long that stain has been there and that RESULTS MAY NOT BE IMMEDIATE.  The longer the time the oil has been on the concrete, the more difficult that it will be to remove.

Initial Treatment of stains:

  1. Pre-treat the surface with one part Oil Sponge UC+ or HD and five parts warm water (105º F).  If you cannot warm the solution, then use the solution cold, both products have excellent cold water cleaning capabilities.
  2. Let it soak for a minimum of 5 minutes.
  3. After 5 minutes, use mechanical agitation with a stiff bristled brush to loosen oil and soils.
  4. Recover liquids using a mop, vacuum system or absorbent material.

Daily Maintenance:

Mop Bucket and light soils- Use a dilution ratio of 1:20-1:50 of Oil Sponge UC+ (dilution rations may vary) and mop as required.

Mop Bucket and medium soils- Use a dilution ratio of 1:10-1:20 of Oil Sponge UC+ (dilution rations may vary) and mop as required.

Mop Bucket and heavy soils- Use a dilution ratio of 1:3-1:5 of Oil Sponge HD (dilution rations may vary) and mop as required.

  • The same dilution ratios can be used in mechanical walk behind systems.
  • A microbial bio-tab may also be added to the solution to further enhance drain-line/ disposal methods.

It is important to respond to spills immediately to minimize surface contamination. 

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