Those that are visible feature flat patches of color, stripes, passages of loose paint - handling, and large areas of blank canvas. (artnews.com)
The acid may not be enough by itself though which is why I recommend a wire wheel or similar device to remove as much rust and loose paint as possible. (mechanics.stackexchange.com)
«Choosing the right materials can make a big difference in how loose your painting turns out,» the artist says. (artistsnetwork.com)