Scotland made the early running and a break from Jonny Gray nearly put the visitors through for the opening score in the first few exchanges.
The clash at Colwyn Bay's Stadiwm Zip World drew a bumper crowd and they were treated to a dominant performance from the Welsh side, which featured RGC star Sam Wainwright who started the contest.
"There was definitely a quiet confidence in the squad, they have been outstanding in their preparation and we went in the game expecting to win reasonably comfortably".
Halfpenny scored a try of his own in the 12th minute and added a second in the 61st minute and Steff Evans scored Wales' fourth try in the 73rd minute as Warren Gatland's men overran the visitors.
Halfpenny had gone five years and 38 matches since his last try in Welsh colours, but this was a day when absolutely everything went right for the Scarlets full backs and his team-mates. The conversion made it a personal tally of 22 for Halfpenny in Wales' 27-0 lead.
Scarlets winger Steffan Evans secured the hosts a bonus-point try with seven minutes remaining with a blistering finish in the corner.
Scotland, who face Wales in the competition's opening game on Saturday, are viewed as serious challengers for this year's title, with a number of key players approaching the tournament in good form.
Time will tell, but this was an encouraging start whereas the result doused the feelgood factor surrounding Scotland in the build-up to the tournament.
Wales began the second period in untroubled mode, as two Halfpenny penalties during a five-minute spell took them 20 points clear before Scotland boss Gregor Townsend made a triple substitution, including an appearance for scrum-half and former Test captain Greig Laidlaw.
It was a ideal afternoon for Wales but there was one man who was nervous in the stadium - defence coach Shaun Edwards.
Scotland was being blanked until the second-to-last minute, when replacement centre Peter Horne crossed.
The Scots haven't really discussed Wales' catalogue of injured stars and Barclay thinks numerous Welsh will be motivated to prove a point.
Wales: L Halfpenny, J Adams, S Williams (O Watkin 70), H Parkes, S Evans, R Patchell (G Anscombe 62), G Davies (A Davies 65), R Evans (W Jones 50), K Owens (E Dee 62), S Lee (T Francis 50), C Hill (B Davies 55), AW Jones (captain), A Shingler, J Navidi, R Moriarty (J Tipuric 64).