Larsen is sometimes credited with inventing the WD-40 formula in 1953 but this is not certain. The WD-40 company website and other books and newspapers credit him but according Iris Engstrand, a historian of San Diego and California at the University of San Diego, it was Iver Norman Lawson (also an engineer born in Chicago at around the same time as Norm Larsen), and the names became confused over time. The formula was kept as a trade secret, so no patent was ever filed listing inventors.
Larsen left Rocket in 1958 after a verbal agreement between Rocket and a distributor fell apart; the distributor set up CRC Industries in Philadelphia to directly compete with Rocket and Larsen left to lead it. CRC was originally called Corrosion Reaction Consultants, Inc. Its first product was called CRC Corrosion Inhibitor, also called 5–56.
By 1968 Larsen had left CRC and had founded a company called Surcon, Inc. headquartered in Collegeville, PA, which also had developed a chemical anti-corrosion formula eventually called "Free 'n Kleen"; the company used it to remove corrosion from the wreck of a Spanish galleon found off the Florida coast. By 1970 the product was being used by Sikorsky Aircraft Corp in its helicopters and was also used by the military to keep machine guns working.
Larsen died in December 1970 at home at the age of 47, of an apparent heart attack.
- "Norman B. Larsen, 47, Surcon President Dies". Pottstown Mercury from Pottstown, Pennsylvania via Newspapers.com. 4 December 1970. p. 2.
- Engstrand, Iris H.W. (Fall 2014). "WD-40: San Diego's Marketing Miracle" (PDF). The Journal of San Diego History. 60 (4): 253–270.
- "WD-40 History - History and Timeline". WD-40 Company. Retrieved 10 April 2017.
- Bobby Mercer (March 18, 2011). ManVentions: From Cruise Control to Cordless Drills - Inventions Men Can't Live Without. Adams Media. pp. 181–. ISBN 978-1-4405-1075-5. Retrieved June 28, 2013.
- Martin, Douglas (22 July 2009). "Obituary: John Barry, Popularizer of WD-40, Dies at 84". The New York Times.
- "The CRC Story" (PDF). CRC Industries. Archived from the original (PDF) on 4 May 2006.
- Industrial Research Laboratories of the United States (10th ed.). National Academies. 1960. p. 129.
- Dougherty, Joseph E. (5 December 1968). "Company Restoring Pieces of Wrecked Spanish Ship". Hanover Evening Sun via NewspaperArchive. p. 25.
- "Surcon Inc Manufacturers of Free 'n Kleen Products". Pottstown Mercury from Pottstown, Pennsylvania via Newspapers.com. 15 November 1969. p. 55.