Junior Chipolpolo have conceded seven times in their four matches in South Korea and have not kept a clean sheet.
Banda, who plays for Zambian champions Zanaco, says the defence has been working hard to remedy that.
"We're looking forward to the game against Italy and we are sure can keep a clean sheet," he insisted.
Mangani says the team has forgotten about their thrilling 4-3 win over Germany in the round of 16, which was decided in extra-time thanks to a Shemmy Mayembe goal.
Zambia had conceded two late goals in normal time that meant at the end of 90 minutes it was 3-3 and so forcing the extra-time.
"As for Germany, it's now water under the bridge. We have buried that chapter and we are looking at Italy," he insisted.
"We take a game at a time, now we are focusing on the Italy game. Each game is very important for us.
"We prepared very well, and so far the tournament has been good for us as a team and for me as as an individual."
Mangani was voted Golden Glove winner as Zambia won a first ever Under-20 Africa Cup of Nations title on home soil earlier this year as he conceded just twice in the tournament.
He is hoping a good run at the Under-20 World Cup will also boost his chances of playing first team football with Zanaco, where he is currently third choice keeper.
Zambia goalkeeper Mangani Banda is determined to keep a clean sheet when they face Italy in an Under-20 World Cup quarter-final on Monday.