Corpuz carded a five-under par 67 after she birdied on four of the first five holes at the Club at Carlton Woods near Houston but was forced to share the lead after a missed putt saw her settle for par on the final hole.
"Been playing really solid these last three days," the 25-year-old said in a televised interview. "I've just been trying to tell myself, you know, get more comfortable in contention, just keep learning from every experience."
Six birdies and a bogey on the par-5 four saw Yin (67) equal the effort, though a bit of good old fashioned luck helped, as her tee shot on 12 inexplicably bounced off the water hazard and onto the bank.
"Extremely shocked," said Yin "I thought I was going to get the card for that."
Neither of the two players has won on the LPGA tour before and both are hoping to hoist their maiden major title on Sunday.
"I know where my game is at," said Yin. "I know how it's been performing for the last three days and the game plan for this golf course, and it's been working well.
"All I need to do is just get my energy back to semi-decent level, and then I think I'll be good to go."
South Korean Amy Yang put herself in a strong position when she carded a seven-under-par 65, sharing a three-way tie for third with American Megan Khang (70) and Switzerland's Albane Valenzuela (68), who drained a long putt for a birdie on the final hole.
Yang has 19 top-10 finishes in the majors and reminded the field why she is a perennial contender at the Club at Carlton Woods near Houston as she produced five birdies on the front nine and only a single bogey on the par-four 11.
"It was one of those days - everything felt so easy and everything felt in sync," she said in a televised interview.
"I just did my best out there, (was) patient and just had fun."
She sat one stroke back from American Allisen Corpuz (25), who had the lead of 10-under par at the 14th hole, and was tied with Megan Khang (25), whose putt lipped out for a bogey on the par-five 13th.
South Korean Chun In-Gee (28) got the crowd going with an ace on the par-three 17 after starting on the back nine but has a lot of ground yet to cover after carding a disappointing six over par in the opening round of the year's first women's major.
The second round of the tournament wrapped up early on Saturday after organisers were forced to halt play due to darkness.
The start of Friday's action was delayed two hours due to torrential overnight rain.
South Korean Kim A Lim (28) was at the top of the leaderboard through 36 holes but appeared to have lost some of her brilliance on Saturday with a double bogey on the par-three third and a bogey on the par-four fifth hole.