|If this were my car, I wouldn't pour acid on it!|
1957 Ford Thunderbird
But the door frame was another matter - how do you remove concrete from a painted plastic panel? One of the hosts suggested a simple rubber mallet, but the other mentioned muriatic acid (HCl, or hydrochloric acid). He posited that the acid would seep in and dissolve the concrete, while leaving the underlying paint relatively untouched. The title of this post (see above) summed up his final comments to the caller.
Of course, you might not want to pour HCl over your hood, or the undercarriage...I'm sure mufflers, battery terminals, and engine blocks don't hold up too well to this home remedy!