They use IP Plating which stands for Ion plating.
" Luv Aj Baby Amalfi Tube Hoops Gold.5 mm)Tubing is 4.3 mm wideEach hoop weighs 4 grams (considered lightweight)Earrings are 100% nickel-free and cadmium-free.1 micron of 18K Gold or Silver, plus e-coating which qualifies it to pass waterproof tests.