Jurors acquitted Damita Devonna Peak and Norris Lazarus Walker on 20 counts of aggravated assault, finding them guilty on a lesser charge of battery.
Superior Court Judge Steve Jones sentenced both to 40 years in prison, without probation.
The verdict ended a 10-day trial in which jurors heard six days of testimony from witnesses and the defendants themselves.
Peak, 36, and Walker, 39, told jurors they punished the boy because he constantly got in trouble and didn't respond to traditional forms of punishment.
They had each faced a possible life sentence, charged with a total of 82 felony counts.
Neither expressed remorse to the judge for what they did to Peak's son, now 13 and living with his younger brother with an area foster family.
Jones told Peak and Walker this was the worst case of child abuse he'd presided over, except for one in which a man and woman were convicted of murder for beating a 10-year-old boy to death a dozen years ago.
"You don't have to have a law degree, you don't have to have a medical degree, you don't have to have a high school diploma to know that was wrong," Jones told the defendants.
"It just disgusted me," he said.