Both were part of the 4x100m relay side that won silver at the Games earlier this month.
While Walaza won his semi-final in a time of 10:33 to qualify third fastest for the final, Nkoana was quicker and qualified second fastest in 10:30, despite finishing second in his semi-final behind Thailand's Puripol Boonson.
The final will take place at 01:47 (SA time) on Thursday morning.
There is also South African representation in the final of the women's 100m, which takes place 01:30 (SA time) and will see Viwe Jingqi compete out of lane 9.
On Tuesday night, meanwhile, South Africa bagged a silver medal when JL van Rensburg finished second in the men's shot-put with a personal best throw of 20.74m.
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