The Pumas could not once breach the Bok try-line at Nelson Mandela Bay Stadium on Saturday, while South Africa scored three tries, earning them a bonus point according to tournament rules.
Two five-pointers came in the first half and another late in the match, when debutant replacement scrumhalf Jaden Hendrikse raced over in the corner minutes after replacing Cobus Reinach, who scored the opening try of the match.
Flyhalf Elton Jantjies also kicked accurately and five successful penalty goals compounded the pressure on the South Americans.
The first-half tries by Reinach and Aphelele Fassi and the boot of Jantjies eased the Springboks into a 21-9 lead at the break and they continued that dominance in the second half, with another top notch defensive display that would have pleased Jacques Nienaber and his coaching staff.
The numerous changes in the Springbok squad seemed justified early on, with the home side looking energetic in chasing the high kicks and stopping Los Pumas attacks with enthusiasm.
The home side started strongly. Jasper Wiese, who was sublime all match in kick receive and returns, came charging through following a Pumas up and under from their own 22 resulting in good front foot momentum to the Boks. Argentina had to go south to stop the Bok maul and were penalised. Jantjies kicked the first penalty goal two minutes in and the Boks were on the board.
That early burst of action was soon replaced by the typical test match grind both teams are well known for. Huge hit followed huge hit as ball carriers tried to get gain line meters, with the high ball contest also providing some variation in play.
No real advantage seemed to be gained from this, with both teams chipping away at the opposing defences, hoping for a wicked bounce, knock-on or loose ball to use to their advantage.
That came South Africa's way in the 14th minute. The Pumas dropped a pass in a backline move and in a flash Reinach was on it and speeding towards the try line. So fast, that the visitors’ defence failed to chase him down before the line as the Bok scrumhalf raced all of 60 meters for his solo effort and an eighth Test try. Jantjies slotted the conversion and the lead was 10-0.
That was immediately cut by three though, with Nicolas Sanchez kicking a penalty goal soon after when the Springboks sealed off the receiver.
But the Springboks struck back immediately.
They kicked deep and high and the Pumas lost the contest, with Eben Etzebeth imperious in the air. It was sent backwards to Jantjies who delivered a pin-point cross kick to Fassi on the left wing.
The speedster juggled the ball and had the left hand touchline to content with, but dotted down for his second Test try. Jantjies could not convert from a tight angle and after 20 minutes, the home side were 15-3 up.
The Springboks were starting to find their rhythm and the Pumas defence and discipline wilted. Jantjies kicked a second penalty goal from straight in front after the Pumas made an early tackle on Jesse Kriel, on the charge from a good running line.
Frans Steyn then launched a long-range effort as the Puma scrum was penalised, but it missed to the left.
The South Americans were playing most of the match in their half and lost a bit of composure as well, falling foul to referee Andrew Brace. The Boks used those opportunities to kick for field position, but a missed lineout throw gave the Pumas an escape route from close to their line.
They worked their way up field and Sanchez added to his tally with another penalty goal after Brace pinged a Bok defender for not rolling away.
It took three points away from the Bok lead, now 18-6 after 35 minutes, but that was cancelled out immediately as the visitors went offside at the resulting restart and Jantjies slotted a third penalty goal for a 21-6 lead.
Sanchez kicked his third on the buzzer, with the teams going into the changerooms with a 21-9 score line.
The Pumas came out strong in the second half, clearly deciding to keep ball in hand and testing the Bok defence and breakdown discipline.
It gained results immediately as South Africa were penalised for not getting out of the tackle ball area quick enough and Sanchez kicked a fourth penalty to cut the lead to 21-12 with 43 minutes played.
Nienaber went to his bench early in the half, replacing his front row players Wilco Louw with Vincent Koch and debutant Joseph Dweba with Malcolm Marx. They made an immediate impact in their first scrum, earning a penalty. Jantjies had a solid strike, and the lead was back to 12 points (24-12).
A second scrum penalty followed soon thereafter and Frans Steyn had a go from 55 meters, but again could not find the direction, pulling it to the left.
Ox Nche was next to get a well-earned rest, being replaced by Trevor Nyakane and the Bok scrum dominance continued.
Marco van Staden was on soon after, in place if Siya Kolisi, and the fresh legs started paying dividends. A good Bok attack was stopped, but illegally so and Jantjies could kick penalty number 54 in the Bok jersey to ease the lead to 27-12 after 60 minutes.
The squeeze was on for the Boks and they started to apply serious pressure on the Pumas line. A lineout drive was stopped by Argentina, but with ball carriers coming in waves, the next pass was always going to have the possibility of a try. This seemed to happen with Fassi going over on the left hand side, but Marx was deemed crawling earlier in the move and the try was disallowed.
Morné Steyn replaced Jantjies and Jaden Hendrikse debuted for Reinach with 10 minutes left.
The former Junior Bok scrumhalf decided to follow the man he replaced and a dash to the line resulted in him scoring a point for every minute he was on the field.
That sealed the win for South Africa, although the Pumas had one more surge to the line following an attacking lineout, but they lost the ball a meter from the line, much to the delight of the Springboks.
South Africa 32 (21) – Tries: Cobus Reinach, Aphelele Fassi, Jaden Hendrikse. Conversion: Elton Jantjies. Penalty goals: Jantjies (5).
Pumas 12 (9) – Penalty goals: Nicolas Sanchez (4).