Most of the aluminum Claudia Wentworth’s company uses to make rooftop solar panel racks in Walnut Creek comes from the United States.It is precisely the kind of American product that Pres. Trump’s new tariffs on imported steel and aluminum are designed to protect.But while the tariffs, imposed by orders that Trump signed Thursday, may benefit domestic metal producers, they will raise costs for Wentworth’s company, Quick Mount PV. Aluminum prices, she said, are already rising.