Why several navies joined China coast piracy patrols

Were navies besides the Royal Navy involved in counter-piracy around China?

Yes; several powers participated, and the mission also justified maintaining forward naval presence in a politically fragmented region.

Piracy gave foreign governments a public explanation for forward-deployed ships during nominal peace. American, French, Japanese, Chinese, and British units could cooperate when interests aligned, even though the powers remained strategic competitors. Openly naming concern about Japan, the United States, or another power would have been diplomatically awkward. Counter-piracy instead made presence appear treaty-based and protective of commerce. For Britain, completely eliminating piracy could therefore have weakened one argument for keeping the China Squadron comparatively strong at Hong Kong, Weihaiwei, and nearby stations. The answer exposes how a genuine policing mission could also serve strategic positioning.