White stains on concrete, SP or Oxalic Acid?

Newbie Questions
1

Hello,

I recently cleaned the bare wood posts holding up my porch above my concrete patio. I used a 2-step wood cleaner and brightener made by Messmer’s (wood finishing products). The first step is a mixture of Sodium Percarbonate (1/3 cup of powder per 1 gallon of hot water) brushed on liberally with a stiff brush, let sit for 15 minute, then rinse well with water. Step 2 (while wood is still wet) brush on liberally Oxalic Acid Dihydrate (1/3 cup powder per 1 gallon of hot water), scrub with stiff brush, let sit for 15 minutes, and then wash off.

I rinsed and rinsed the posts after the second step and washed the concrete. When the concrete dried there were white “stains” in the concrete. Were these caused by the SP or the Oxalic Acid? What is the recommended remedy to remove them? The concrete is un-sealed.

You can’t see them when the concrete is wet, but no manner of rinsing, scrubbing or power washing has removed them. I have’t tried anything except water in the power washer (no other cleaning chemicals), I wanted to get other’s opinions first, before I potentially made the problem worse.

Thanks in advance.
Daniel.

2

It’s the Ox. It’s used for brightening concrete and removing stains. Just spray on rest of concrete and let sit a little while, wash off and the concrete should all match

2 Likes
3

Hello Rick,

Thanks for taking the time to respond, that is very helpful.

Daniel.