Sub-One Technology, a Pleasanton start-up that provides a way to coat pipes with protective materials to better serve the oil, gas and ethanol industries, has raised $7 million in a second round of funding.

The technology is significant, the company said, because it provides a way for the energy industry to retrofit pipes and other products it uses for exploration and transport, coating them with protective coatings from the inside. It does this using a gas and a vacuum process.

Andrew Tudhope, CEO of Sub-One Technologies, said his company has been “hammered” by requests from the oil and gas industry for his products, and so wanted the money to expand quickly to meet the demand.

The company is focused on serving pipes that transport liquids such as oil, ethanol and natural gas. Its product has become attractive to the oil industry because oil deposits have increasingly become sour and corrosive as oil companies dig deeper into the earth to extract them, Tudhope said. Instead of using expensive titanium pipes to find natural gas, as Chevron is doing off the coast in Australia, Chevron can coat lower cost carbon steel pipes with Sub-One’s product, he said.

Advanced Technology Ventures (ATV) led the round, while existing investors Chevron Technology Ventures and ITI Energy participated. Wes Raffel, General Partner at ATV and David Lam, Chairman of the David Lam Group, will join the company’s board of directors.

There are 2.1 million miles of pipelines in the U.S. alone, transporting natural gas, crude oil, petroleum and other products, and the coating market for these pipes is about $500 million, according to ATV’s Raffel.

This is ATV’s fourth investment in the clean tech area, the other ones being coal gasification company GreatPoint Energy, photovoltaic company Calisolar, and one that is still in secretive mode.