I agree with lclevel; you need the help of experts. Also contact the primer's manufacturer to find out if they have a specialized removal product, and get their suggestions specifically for stain removal from concrete.

I suspect the finished-stain portion will show a difference in coloration over the primed areas due to the primer soaking downwards, probably bonding literally *into* the cement. And you have a valid concern about how any finish will adhere to the primer-soaked areas which should be discussed with the manufacturer of the finish.

I had something similar happen with my HVAC guys. I could have strangled them. Acetone did the trick for me and I think it is an approved product for concrete staining. However, I would use it very carefully. I used a very dark brown to stain my floors and I don't notice the removed pvc primer spots. They are there, but I have to nearly put my face at the floor to see them. The stain actually doesn't adhere to the concrete (assuming you are acid staining), but it reacts with the components of the concrete slab. The spots did take some stain, although they are more really dark gray than brown.

Even worse than the pvc primer is the stains left from where the electrician dropped staples and they rusted. I tried to pick up all the nails and staples, but I missed some. Those spots are very noticeable. Definitely get yourself a long handled magnet and keep all the nails and staples off the bare concrete.

Thanks everyone for all of your ideas, the company says they are researching ways to get this up (they even spilled some on their own concrete to test it), but I don't want to count on them to fix this, and I certainly don't want to look at the spots for the rest of my life! Dannie gal, thanks for your suggestion, we will have to try the acetone in the mech room. We're planning on doing the acid staining so hopefully we're as lucky as you and they won't be very visable!

Also good point on the rust issues, I've been very careful to pick up anything that might rust just in case that would show through the staining. I guess the lesson to learn from this (it's a little late for us, since we won't have any more subs in at this point), put large signs everywhere near your slab if you're going to stain it so everyone knows they need to be very careful!

After doing some research in some literature I have, it says do the following for cleaning PVC primer:

Step 1. Clean with Acetone or alchol
Step 2. Use a paint stripper.
Step 3. Clean with TSP.

This is an easy one. When we at work (plumbing and heating) spill some purple PVC primer, we just use CPVC Primer to pick it up. Works like a charm.

While there are many options available to remove the stain, one must be careful to choose a solvent that will not impede the acid stain from properly reacting with the concrete. One wrong solvent choice and you have a much larger problem when the stain doesn't take.

I seem to remember (although it's been 18 months since I did it) scraping a putty knife across the spots popped the primer dots off the floor. Acetone definitely worked though. I remember being worried because the only acetone item I had with me was fingernail polish remover! It was the gel kind in the little pump bottle. I was nervous at first because it was "enriched with Vitamin E" and I didn't know what that would do to the concrete! The pump was handy though because I was able to be very neat with it! I'm glad none of my subs were around to see me pull out fingernail polish as my weapon of choice! :D

Followed this thread and had to laugh. A lot of advice from well meaning posters of conventional consensus wisdom copied right out of instruction manuals. The manufacturer is researching the problem? You got to be kidding, as if this doesn't happen every day and the company hasn't been asked this a million times from consumers. Allow me to relate some actual facts and just one solution to "stains" from purple PVC cleaner. I just had some purple PVC cleaner leak onto an unsealed travertine pool deck. Knowing that most dyes and stains are organic compounds, and that nothing reacts faster to bleach than organic substances, I took a piece of travertine and "stained" it with purple cleaner. After allowing it to sink in and dry, I applied straight Clorox bleach to the stain. After about 10 minutes, the stain was about half gone. After a second application of bleach onto the stain, after about 1/2 hour it was completely gone, and there was NO damage to the travertine. The same results should be expected from concrete as well. Dems da facts!

You do realize this post is almost 11 years old..........................

Yep, but the issue itself is timeless, still relevant, and one of the first hits in an internet search for solutions to the problem. The perfect place for such information. While of course the original post query has long ago been resolved, the purpose for such forum discussions to continue to remain rather than to be deleted years ago is to help others in the future. Otherwise, what are we doing here anyway?

Acetone might dissolve the stain enough to all it to be washed with a strong detergent.

If you can't remove it. If it can't be removed, you can apply a solid floor finish over the concrete. In my opinion, that would be a major an improvement in terms of appearance, comfort and ease of maintenance.

Used the cpvc cleaner- worked perfectly