Multiple world and Olympic champion Kozak, returning this year to the single seat after taking a break to race multi-seat disciplines in the last two years, recorded 1:54.241s.
Litvinchuk was second fastest into the final, followed by German Franziska Weber (1:56.515) with Dane Emma Jorgensen fourth overall in 1:55.193.
"It was pretty tough out there," Carrington said. "The competition is incredibly strong, you have to be at your best."
Carrington was pleased with the way she handled her day, coming down from the emotional high of yesterday's gold medal performance.
"I was really surprised how I could just turn around. Experiencing yesterday I got on a bit of a high, then coming down was a contrast, quite different.
"But it's almost like this is what I've prepared for and having to come back and do the heat and semifinal really grounded me again."
Her coach Gordon Walker was impressed with how Carrington handled the day. He was impressed with the manner of today's performances, and while "winning gives you a better lane but it's just about tomorrow (the final). I think she did a good job," he said.
Walker doesn't believe the final is particularly wide open. Sustained class over a long period of time suggests there are only a handful of racers who can win tomorrow, in his book.
Inna Osipenko-Rodomska, the bronze medallist behind Carrington in the K1 200m final yesterday, won 500m gold eight years ago; Kozak achieved that in London in 2012.
"You're talking about a group of athletes who have been around a long time, a bit like the men's single. It's very hard to get to that level. It may be open for some of the lower medals or placings, but definitely not for the top end. It's pretty clogged up."
Put Carrington in that elite group. But by Walker's measure, there's likely to be four, no more than five, paddlers battling for the medals.
Throw seasoned German Weber in there, along with Kozak, Osipenko-Rodomska and Litvinchuk. Plus, of course, Carrington.
She won the world K1 500m crown last year, but Kozak's return has lifted the game.
If Carrington wins gold, she will become the first New Zealand woman to bag three Olympic gold medals, and will join boardsailor Barbara Kendall (gold in 1992, silver in 1996 and bronze in 2000) and shot putter Val Adams (gold in 2008 and 2012 and silver in Rio) on a total of three medals.
Only five New Zealand athletes, all men, have won two or more medals at a single Olympics - running legend Peter Snell, kayakers Ian Ferguson, Paul MacDonald and Alan Thompson, and swimmer Danyon Loader.
"It's great she's into another Olympic final," Walker said. "We've seen a few world champions not even make finals. She should be proud of herself."
