They are almost the same, but not quite. Scrubbing means to rub something to clean it - usually with a brush. Scouring means to clean, or to wear down a surface by abrasion. Scrubbing describes an action, but if brushing isn't enough, the surface will remain dirty. Scouring implies that the methods are enough for the job, and they can be anything. For example, many rocks in the Sahara desert are scoured by the wind. That means they actually are worn smooth, and it is because of the wind. Scouring a person or animal would be very cruel.

Both scour and scrub mean to clean something by rubbing it hard. These words are synonyms. Typically you can scour "something", but you would scrub "something or someone". He will scour the bathtub. He will scrub the bathtub. He will scrub the dirt off of his feet.

I agree with Jim. They are not synonyms. 'Scrub' refers to a rapid or repeated rubbing action. If your hands are dirty, from gardening or car maintenance, for example, you'll need to scrub them - perhaps with a brush - to get them clean. 'Scour' is different. It is a deep abrasive action. If a cooking pan has thick, burnt-on residue, you might have to scour it, perhaps even with some kind of chemical product.

what Julia said is correct.