Rain-X is a line of consumer automotive and surface care products produced by SOPUS Products (formerly Quaker State), a subsidiary of Royal Dutch Shell. Industrial Rain-X products were produced by Ecolab and used in carwashes and other industrial applications. Ecolab sold its vehicle care business to Zep Inc. in 2012. The most well known Rain-X product is a synthetic hydrophobic surface-applied product that causes water to bead, most commonly used on glass automobile surfaces. Rain-X was originally registered as a trademark in 1972 by Unelko and sold to Quaker State in 1997. Rain-X branded products are distributed by Shell Car Care International Limited in the U.K.
Due to its general water repellent properties, the original Rain-X formulation is used in a wide variety of consumer, commercial and industrial settings. The primary use of Rain-X is for automotive applications. Commercially sold "Original Glass Treatment" is the original and most well known Rain-X branded product. It is a hydrophobic silicone polymer that forces water to bead and roll off of the car, often without needing wipers. It is sold in 3.5 or 7 oz bottles, or as wipes or towelettes.
Rain-X Online Protectant was introduced to carwashes in 2005. It is a water-based compound that is applied to the entire car's surface, working much like consumer grade Rain-X products. On December 1, 2012, the Ecolab vehicle care business was sold to Zep Inc. The sale included the Black Magic, Blue Coral, Rain-X, Zep Enviroedge, Niagara National, Washtronics and Armor All Professional brands.
The original coating has also had use in military and other government settings. The Australian Military has examined the effect of application of Rain-X and similar products to submarine antennae to improve signal transmission, although other coatings had longer-lifespans when submerged in salt-water.
Ski and snowboard enthusiasts use Rain-X as "wax" to effectively overcome sticky wet snow common in spring conditions. While skiing or riding on mountains with hard snow pack, the heat of the sun changes snow conditions starting on the lower slopes. Skis may suddenly slow down, throwing one off-balance, because of a change in surface tension, a sort of "sandpaper effect." Rain-X is applied to the ski or board base, or to the bottoms of ski boots to reduce, or eliminate snow "wedges" that interfere with proper mounting into ski bindings.
Rain-X's primary active ingredient are polysiloxanes, the primary one being hydroxy-terminated polydimethylsiloxane. The polysiloxanes have functional groups that bind to the hydroxyl group of the glass surface.
- SEC filings, 18 June 2007 - EX-4.7 of S-8 POS for Royal Dutch Shell plc
- http://www.ecolab.com/Businesses/VehicleCare/rainx.asp Archived 23 February 2009 at the Wayback Machine.
- "Ecolab Introduces New Rain-X® for Wheels for the Professional Car Wash Industry". Ecolab. 6 December 2010. Retrieved 8 December 2014.
- "Zep Inc. Completes Acquisition of Ecolab's Vehicle Care Division". Zep Inc. 3 December 2012. Retrieved 8 December 2014.
- U.S. Patent and Trademark Office, Registration statement, Serial # 72416424, registration # 0960701 searchable at 
- Kenneth W. Whitten, Raymond E. Davis, M. Larry Peck, George G. Stanley, Chemistry, Cengage Learning: 2009, p. 459
- Jim Dimas, Andrew J. Scardino, John A. Lewis, "Enhancement of Drain-Down Capabilities of Submarine Antennae", DSTO-TR-2012, 
- Pierce, Scott M.; Chan, Kwaichow B.; Zhu, Heping (2008). "Residual Patterns of Alkyl Polyoxyethylene Surfactant Droplets after Water Evaporation". Journal of Agricultural and Food Chemistry 56 (1): 213–9. doi:10.1021/jf072372y. PMID 18069796.
- Otobe, K. (2001). "Behavior of DNA fibers stretched by precise meniscus motion control". Nucleic Acids Research 29 (22): 109e. doi:10.1093/nar/29.22.e109.
- Cong, Hailin; Hu, Xudong; Radosz, Maciej; Shen, Youqing (2007). "Brominated Poly(2,6-diphenyl-1,4-phenylene oxide) and Its Silica Nanocomposite Membranes for Gas Separation". Industrial & Engineering Chemistry Research 46 (8): 2567. doi:10.1021/ie061494x.
- James M Schaefer,"Sliding in Spring Snow," Snow Pro -- The Official Publication of the Professional Ski Instructors of America Educational Foundation, Albany, NY, forthcoming.
- Timothy Michael Shea, "Durable hydrophobic surface coatings using silicone resins", US Patent Application # 7344783 B2, description 4.