Ukraine
I was a Boatswain Mate on the USS Santa Barbara stationed in Goose Creek SC. A Pnuemtic needle gun is not used to remove "rust". It;s used to remove old paint. And there is no 1st coat of paint. 1. Needle gun 2. Sander. 3. Primer. 4 1st and only coat of "haze gray"
Yeah it's better to not pile up the paint. Paint burns too hot.
I sure saw a whole lot of rust being removed with needle guns. Especially in the corners. A hole lot of paint as well.
Right now I'm rebuilding two Ford tractors with my neighbor. One is mine and one is his. I'm using Lye in a boiling dip tank for all of the smaller parts of both tractors. MIne is a late 1940's 8N. His is a somewhat larger 641 from the 1950's. It's not important. we're just having fun in the old man way. Puttering together on something.
For the larger frame parts we're using a fine needle gun, and rotary wire brushes. Later I will sandblast the stubborn spots.
I like the way Lye will reduce the rust if one boiles it over and over again in very stout mixtures of water and Lye, pluss scrafical light metals. It chemically reduces the rust with the aluminum and zinc I throw in to boil it with it gets somewhat shiny coated. kind of galvanized like which paint will stick to if one hot water scrubs and rinses it well after using laundry soap with hot water. Lot of soap and hot water helps paint to stick well.
In a 15 gal tank which is heated by a three burner Coleman camp stove which burns white gas, I throw in one pound of 85% Lye, and about one ounce of zinc and two ounces of soft aluminum.
If I have it, I give it a bit of Magnesium casting metal as well. Not a lot, and not large pieces. Right now I have some from an old outboard motor. Those metals are sacrificial, they power a chemical reaction which reduces the rust back into elemental iron. After three or four hours of boiling the sacrificial metal will be dissolved down to little pieces at the bottom of the tank.
I boil the parts for four hours and then allow them to cool down overnight, then drain the tank and wash and rinse the parts.