Peter McCausland is stepping aside as president and chief executive of Airgas Inc., the Radnor company he founded 30 years ago, built into the largest of its kind, and steered through a high-profile takeover fight that ended 14 months ago, the company said Thursday.

After Airgas's shareholder meeting in August, McCausland, 62, will become executive chairman and Michael L. Molinini, 61, currently executive vice president and chief operating officer, will be promoted to president and CEO.

The move is a key step in leadership transition at Airgas, but McCausland will retain significant power in his new position and in his continued role as chairman of the company's management committee.

It is not unusual for founding CEOs to have difficulty turning over the reins, but in an interview McCausland said that would not be the case at Airgas because he and Molinini have such a good relationship and have "been in lockstep for the better part of seven years."

Besides, "I'm the biggest shareholder in the company. The last thing I'm going to want to do is interfere with Mike's role as CEO," said McCausland, a lawyer by training who built Airgas into the nation's biggest distributor ofindustrial, medical, and specialty gases through nearly 400 acquisitions.

Molinini, on the other hand, grew up in the packaged gases business, working as a teenager for his father's business in North Jersey that did analytical work for specialty gases producers.

"I've been around cylinders since I was 15," he said.

After graduating from Seton Hall University with a chemistry degree in 1972, Molinini worked for two other companies in the industry before landing at Airgas in 1997.

Molinini, charged with explaining the nuts and bolts of Airgas's operations to investors, was a key figure during the takeover fight with Air Products & Chemicals Inc., which became public in Feb. 2010 and took a rancorous turn through the Delaware Court of Chancery, where Airgas's antitakeover defenses prevailed.

Air Products, an Allentown company that is a major producer of the gases that Airgas distributes in small quantities, went public with a bid of $60 per share, raising it to $70 per share before a court ruling convinced it to withdraw the offer on Feb. 15, 2011.

Since then, Airgas shares have gained 42 percent, closing Wednesday at $91.23. Over the same period Air Products shares are down 4.5 percent.

Separately on Thursday, Airgas reported strong fourth-quarter financial results, with sales up 11 percent at locations open more than a year and earnings per share up 26 percent, excluding certain unusual items, such as last year's expenses related to the unsolicited takeover attempt.

Revenue for the year ended March 31 was $4.75 billion, up 12 percent. Full-year adjusted earnings per share were up 23 percent, to $4.11 from $3.35, Airgas said.

The company's shares were up 45 cents, to $91.68, in early trading on Nasdaq.

McCausland said the improved U.S. economy and the momentum at Airgas were among the factors that made this a good time for him to step back a bit, focusing on growth strategies and several other areas.

"I have tremdendous confidence in Mike. If I didn't, I wouldn't be dialing back at this time," McCausland said.

He said that the amount of time he devotes to Airgas would decline only a little.

"I would like to take a couple of trips — 10 days, a couple of weeks — without being on my BlackBerry 24-7," he said. "Some people don't believe I can do that."

Contact Harold Brubaker at 215-854-4651 or