Nigel Davies' men followed up on their last-minute heroics against Connacht to register their second bonus point win in this season's Magners League.
Jonathan Davies' hat-trick of tries was the highlight, with fellow backs Andy Fenby, George North and Martin Roberts also crossing the visitors' whitewash. Stephen Jones' assured place-kicking helped him to 19 points.
The first half took some time to catch fire. Jones' early brace of penalties saw the Scarlets take a 6-3 lead, with Aironi fly-half Ludovic Mercier kicking one of his three attempts on goal.
The game, which had been blighted by handling errors and indiscipline at the breakdown, opened up before half-time as the Scarlets worked full-back Fenby and teenager winger North over for tries.
The Italian outfit gave way in the 29th minute when flanker Johnathan Edwards exploited a defensive hole.
He transferred the ball to Sean Lamont who was tackled short of the try-line by Aironi centre Gilberto Pavan, but a quick recycle led to Fenby diving over for Jones to convert.
Aironi, who pressed Munster and Ulster in their opening league games, threatened with an immediate interception - but unfortunately winger Danwel Demas was unable to hold onto the ball.
The Scarlets were beginning to find some rhythm and some good continuity from backs and forwards preceded North's unconverted try in the right corner, his third of the season.
The 18-3 half-time buffer was extended by Jones, from a 41st minute penalty, and then the Welsh region really cut loose.
Jonathan Davies took a terrific pass from his centre partner Regan King which invited him to surge through for his first try.
Then the bustling number 12 secured the bonus point for the Scarlets after Aironi flanker Jaco Erasmus had been sin-binned.
The game was broken up by a raft of replacements, but the Scarlets kept pressing for scores and they duly came.
Replacement scrum half Roberts dotted down under the posts after a swift, skilful break from a ruck, and man-of-the-match Davies completed his hat-trick in the 75th minute, using quick lineout ball to force his way through the Italian defence.
Similar to their two previous outings, Aironi finished the game on the attack and Williams, following a series of forward drives, salvaged some pride with a try that Mercier converted.
|Scarlets Score Card|
|Aironi Rugby Score Card|