plane_crazzy Posted July 15, 2012 Share Posted July 15, 2012 I just finished a wind chime hanger that is riveted to a piece of 1 inch square tubing about 6 feet long. I was planning on sandblasting the entire project before moving on to painting, but ran across rust oleum's rusty metal primer. All the metal is hot rolled so even the parts that didn't get heated have mill scale on them. Has anyone tried this product on mill scale? I have the equipment to blast it down to bare metal, but if using this primer can save me a step it would seem like it is worth a shot. Thanks Link to comment Share on other sites More sharing options...
SmoothBore Posted July 15, 2012 Share Posted July 15, 2012 Although I find the durability of most Rust-Oleum finishes disappointing, ... their Rusty Metal Primer is a first class product. It penetrates and seals deeply pitted rust, or weathered cast iron, ... and holds up well, for extended periods. That being said ..... Mill scale is really not the same thing as deeply pitted rust, ... and is easily removed. This is just my opinion, ;) ... but rather than trying to cut corners, I get more satisfaction from doing the best possible job ... regardless of how long it takes. . Link to comment Share on other sites More sharing options...
plane_crazzy Posted July 15, 2012 Author Share Posted July 15, 2012 What is your opinion of their normal metal primer? Link to comment Share on other sites More sharing options...
ptree Posted July 15, 2012 Share Posted July 15, 2012 For rusty metal, I use Extend a product the uses a little phosphoric acid in the mix to convert the rust to iron phosphate, and also is a good primer. I follow with Rust-Oleum Rusty metal primer, the red oxide type, then top coat. For smaller jobs I am fond of Rust Tough acrylic enamel, although at $6.00 a rattle can it is a little high. Works wonderfully though and the Max Flat Black is a deep soft color that beats satin black hands down. Extend can be purchased in a spray can, or a brush on liquid. Permatex makes a liquid as well, since both th Loctite Extend and Permatex are Henkel companies. I prefer the brush on coating, and the Permatex is somewhat cheaper and can be bought/ordered at ACE hardware. I follow the Extend directions to the letter and have found no better system than I have described for deeply rusted metal. Lightly rusted I do the same just in case:) Link to comment Share on other sites More sharing options...
petere76 Posted July 15, 2012 Share Posted July 15, 2012 Metal primer of all manufacture is a porous coating that likes to go on clean bare metal. its designed to encourage a surface coating to adhere, it is not a sealer. Primer failures occuring because of scale are due to the different expansion rates of two dis-similar materials. The seal fails around the scale, compromises the outter coating (seal) and lets in mositure, oxidation does the rest. We use the normal primer on items that are for outside use in the North East region. Cold and hot lots of expansion and contraction and UV exposure. We get the iron down to bare metal and wash it to remove any grease or oils. . Work in a reasonably clean and dust free environment. Don't be grinding on one side of the shop and painting on the other side, this is a formula for frustration. We tripple coat the primer, using different colors to assure full coverage, this way you can see the spots you missed. Multi coat the finish as well. Light coats adherer better and give a better visual appearance. Gloss spray coatings are thicker in ml dimension than flat varients. if you want a flat finish go with gloss for the first coats and final coat with flat, you will get a better mil thickness on your final product. My simple shop calculations show that we spend a lot of time on any given piece in, descaling.surface preparation and coating. It is a good percentage of the cost componet in your production of any piece. Have a good system for descaling (acid wash, wire wheel whatever works for you). Keep it clean . Use good coatings. It also helps if you do batches as opposed to single pieces. Singles have the same set up and take down times on both ends of the process, so you might as well do a batch. Economy of scale favors multiples over singles. Hope this helps. Peter Link to comment Share on other sites More sharing options...
greg Posted July 15, 2012 Share Posted July 15, 2012 Mill scale =rust at some point :angry: I have found it best to remove as much as you can before applying any primer or top coat Link to comment Share on other sites More sharing options...
Dodge Posted July 17, 2012 Share Posted July 17, 2012 I've never seen mill scale on tubing. Hot rolled bar and flats and coiled steel (raw materials) yes. However, pipe and tubing (at least the stuff the company I worked for made) goes through so many rollers and accompanying lubricants, that scale is left on the rollers and shop floors. Those lubricants should be washed off though, because even if they seem intact, they usually don't mix well with paint. Link to comment Share on other sites More sharing options...
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