WD 40 is used for many things, but it might not be the most efficient solution to remove calcium deposits. Acids can quickly dissolve calcium carbonate into their parts.
Most of the leading descalers on the market today are quite acidic, with hydrochloric acid being a typical component.
Therefore, WD-40 is not likely to be a very efficient descaling agent if it does not contain the crucial ingredient. It may even cause difficulties because it will react with certain plastics, dissolving them.
Although some articles and videos on YouTube say that WD-40 can help remove persistent limescale stains, we strongly advise you to proceed with caution and propose that you choose a significantly less expensive and significantly more efficient solution.
The exact composition of WD-40 is a closely guarded secret, but we know that it includes petroleum-based oil and several hydrocarbons. This places it closer to the alkaline than the acidic; WD-40 states on its website that its product contains no acid.