Editing Rust, pitted

{{youcanedit}} {{newarticle}} [[Image:Pitted_rust_before.jpg|thumb|350px|Pitted rust before treatment.]][[Image:Pitted_rust_after.jpg|thumb|350px|Pitted rust after treatment.]] Pitted rust is a common problem when dealing with body panels. The "best" way to deal with it is generously cut it out, and [[patching a body panel|replace it with new metal]]. However, this isn't always practical, so it's frequently handled by mechanically and/or chemically removing the rust, "filling" the pitted areas with a purpose-specific product, and priming. Newer methods introduced to the market include 'spray welding', where molten galvinized metal is sprayed on the rust pitted area until it is covered.[http://www.rustbustersllc.com/rustbustwebmovie.asf]See attached movie on how its done. [[Image:Cab_corner_before.jpg|thumb|350px|Cab corner with pitted rust, before treatment.]][[Image:Cab_corner_after.jpg|thumb|350px|Cab corner with pitted rust, after treatment.]] ==What causes pitted rust?== All bare steel degrades in the presence of water (such as the water in air). Rust '''pitting''' is caused by a localized lack of oxygen in metal. This causes a small area to become anodic (it readily gives up electrons), while the slightly more oxygen-rich surrounding area becomes cathodic (readily accepts electrons), accelerating the local formation of rust. For more details, see [[Rust#What is rust?|What is rust?]] Pitted rust can be more insidious than surface rust. While the pits may comprise only a small volume of a piece of metal, the widespread perforation can compromise the overall structure of the metal. ==How to fix pitted rust== Ideally, any pitted rust is cut out and replaced with new metal. Few situations are ideal, so it's common to remove the rust and fill the pits with one of various fillers, epoxies, or filler-like products. ===Removing the rust in the pits=== First, all visible rust must be removed using one or more of the methods listed below. ====Mechanical removal of pitted rust==== *A spot blaster is useful for this, with silica as the medium ''(confirm, and get list of other acceptable media)''. *Also, the following can be used: metal brush, grinding wheel, die grinder, a wire wheel on a drill. 3M Clean-n-strip discs, Lava wheels. ====Chemical removal of pitted rust==== *Let naval jelly sit on the area, overnight if possible. Cover it with plastic wrap to keep it from drying out. *If it's practical to remove and soak the panel or part, there is also the option of using electrolysis for rust removal or using one of several products that require a rusted part to be completely immersed. * Another alternative is to use phosphoric acid. It is readily available at home centers such as Home Depot under the brand name Phosphoric Plus. It may be brushed on or a part may be soaked in the solution. Heavy pitting will take multiple applications with some wire brushing in between to speed the process. The chemical reaction of the phosphoric acid with iron oxide produces black, water-soluble iron phosphate, which can be scrubbed off. A follow up passivating treatment containing zinc phosphate, such as PPG DX520, can be used to prevent flash rusting. Phosphoric acid rust-removing products may or may not contain zinc phosphate, so read labels and directions carefully. ====DIY electrolytic rust removal for smaller parts==== Things you will need... -1 plastic tub big enough to submerge your gpart. Rubbermaid comes to mind. ...or at least big enough to submerge half of it, and you can flip it and do the other half later. -1 box of WASHING soda (available at any big retail store near you.) -1 strip of scrap steel (NOT stainless. under NO circumstances should you use stainless steel for this method. The electrolytic reaction between the chrome and stainless will create a VERY nasty compound.) Rebar or a metal broom or mop handle would be good. -12v battery charger capable of a constant 2-amp current. (Make sure the clips aren't stainless steel.) -water -steel wool pad With the steel wool, gently remove any surface rust as well as you can without scuffing the metal. In a WELL VENTILATED area.... Take the tub, mix one teaspoon of washing soda for each pint water. Put your grill in the water/soda mix, and hook up the NEGATIVE clip to the grill. The POSITIVE lead should be clipped to the steel rod and set in the water. Don't submerge it, but stand it up in the water against the side of the tub. Set your battery charger to a constant 2 amps...and walk away. You should start to see a fizz coming off your part. This is the electrolytic reaction that will remove the rust. Leave it overnight. Check it the next day. If you're not satisfied, leave it submerged longer. This will even remove hard to get pitted rust, and will not harm the metal underneath. ====Removal with heat==== *Heat the pitted area until it glows, then cool it with oil on a rag. This fix should only be used on small areas because it can warp the surrounding metal, causing wrinkles and shrink marks. ''(confirm that this is acceptable practice, sounds borderline)'' ===Handling rust pinholes=== Rust pinholes can be difficult to repair because the "hole" is usually more like a "crater". The hole itself is at the bottom of a thinned-out, crater-like area of metal. First, remove any rust using the above methods. Then, these methods have been mentioned ''(confirm)'': *Clamp a piece of copper to the other side of the panel, covering the pinhole. Then, fill the hole in with a MIG welder. When done, unclamp the copper -- it won't stick to the panel, and will act as a heat sink, so the panel doesn't warp as much. *Drilling and patching -- explain. *Solder Flowing can be done with specially formulated flux and solder combinations at temperatures as low as 350 degrees Fahrenheit. ==Filling in the pits== Now that the rust has been removed, the pitted area of bare metal has to be filled. First, clean with a wax and grease remover ''(confirm this, and add other cleaning/coating options here)''. Then, the pits are typically filled by priming with a high-build primer, filler or similar product. Generally, the less product used, the better. However, it may be necessary to repeatedly prime and block sand to fill the pits. ===High-build primers and related products=== ''(need more products listed here)'' *[http://www.evercoat.com/productDetail.aspx?pID=171 Evercoat FeatherFill G2] *[http://www.evercoat.com/productDetail.aspx?pID=70 Evercoat FeatherFill] *[http://www.evercoat.com/productDetail.aspx?pID=28 Evercoat Slick Sand] *[http://www.debeerlakfabrieken.com/ti/en/TI1-980GB.pdf DeBeer Polyester Spray Filler] ==Additional resources== *[http://www.materialsengineer.com/G-Pitting-Corrosion.htm Pitting Corrosion] -- MaterialsEngineer.com *[http://www.corrosion-doctors.org/Forms-pitting/Pitting.htm Pitting corrosion] -- Corrosion-Doctors.org *[http://en.wikipedia.org/wiki/Pitting_corrosion Pitting corrosion] -- Wikipedia *[http://www.corrosion-doctors.org/Forms-pitting/shapes.htm Corrosion pit shapes] -- Corrosion-Doctors.org [[Category:Body and exterior]] {{youcanedit}}

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