Rust
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[[Image:Rust at battery tray old versus new.JPG|thumb|300px|A rusted battery tray alongside a new one.]] | [[Image:Rust at battery tray old versus new.JPG|thumb|300px|A rusted battery tray alongside a new one.]] | ||
| − | + | ==What is rust and its causes?== | |
| − | + | Rust is a kind of corrosion -- a decay or breakdown of a material in reaction to its environment. Specifically, rust is an electrochemical corrosion that occurs in the presence of iron, oxygen, and water. Oxygen and water are available in the open air, and iron is the principal ingredient in steel. | |
| − | ==What is rust?== | + | |
| − | Rust is a kind of corrosion -- a decay or breakdown of a material in reaction to its environment. Specifically, rust is an | + | |
For rust to occur it needs an anode (a piece of metal that gives up electrons), an electrolyte (a liquid that helps transport electrons), and a cathode (a piece of metal that accepts electrons). The more conductive the electrolyte, the quicker rust will occur. For this reason, humid air, salty air, or salty water will accelerate the formation of rust. | For rust to occur it needs an anode (a piece of metal that gives up electrons), an electrolyte (a liquid that helps transport electrons), and a cathode (a piece of metal that accepts electrons). The more conductive the electrolyte, the quicker rust will occur. For this reason, humid air, salty air, or salty water will accelerate the formation of rust. | ||
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Other metals besides iron oxidize, but their oxidation is not referred to as rust. For example, when aluminum oxidizes, it forms a protective, corrosion-resistant coating that is similar in appearance to un-oxidized aluminum. Zinc oxidizes similarly, which is why it is used for galvanizing. Only the oxidation of iron and steel is known as "rust". Why? Because iron oxide takes up more physical space than iron. It's bigger. So, when iron and air combine to make Fe<sub>2</sub>O<sub>3</sub>, it "puffs out", exposing even more of the original steel to the elements. | Other metals besides iron oxidize, but their oxidation is not referred to as rust. For example, when aluminum oxidizes, it forms a protective, corrosion-resistant coating that is similar in appearance to un-oxidized aluminum. Zinc oxidizes similarly, which is why it is used for galvanizing. Only the oxidation of iron and steel is known as "rust". Why? Because iron oxide takes up more physical space than iron. It's bigger. So, when iron and air combine to make Fe<sub>2</sub>O<sub>3</sub>, it "puffs out", exposing even more of the original steel to the elements. | ||
| − | There is another iron oxide also referred to as "rust". It's Fe<sub>3</sub>O<sub>4</sub>, commonly called "black oxide", or, in mineral form, magnetite. This is the stuff that's left over after using certain products to "convert" rust. Black oxide takes up the same amount of space as iron, so it doesn't bulge it out, like reddish-brown rust, Fe<sub>2</sub>O<sub>3</sub>. Since black oxide itself doesn't offer much protection against corrosion, it's typically covered up (often with [[epoxy primer]]). Black oxide is an example of a conversion coating, a metal coating where part of the surface is converted into the coating itself, by a chemical or electrochemical process. | + | There is another iron oxide also referred to as "rust". It's Fe<sub>3</sub>O<sub>4</sub>, commonly called "black oxide", or, in mineral form, magnetite. This is the stuff that's left over after using certain products to "convert" rust. Black oxide takes up the same amount of space as iron, so it doesn't bulge it out, like reddish-brown rust, Fe<sub>2</sub>O<sub>3</sub>. Since black oxide itself doesn't offer much protection against corrosion, it's typically covered up (often with [[epoxy primer]]). Black oxide is an example of a conversion coating, a metal coating where part of the surface is converted into the coating itself, by a chemical or electrochemical process. |
===Why do older cars rust more than newer cars?=== | ===Why do older cars rust more than newer cars?=== | ||
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===Tools=== | ===Tools=== | ||
| − | Besides basic hand tools, do you have | + | Besides basic hand tools, do you have an air compressor? Access to a DA sander? Angle grinder with wire wheel? Media blaster? Spot blaster? Blast cabinet? Spray gun? In some cases electric powered tools can be used instead of pneumatic tools. |
===Cost=== | ===Cost=== | ||
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Lots of "rust neutralizers/metal etchers/floor etchers/metal conditioners" contain primarily phosphoric acid, which reacts with rust (iron oxide) to create iron phosphate, a hard black substance over which primer can be applied. | Lots of "rust neutralizers/metal etchers/floor etchers/metal conditioners" contain primarily phosphoric acid, which reacts with rust (iron oxide) to create iron phosphate, a hard black substance over which primer can be applied. | ||
| − | Don't use battery acid (sulfuric acid) for rust removal. | + | Don't use battery acid (sulfuric acid) or muriatic acid (hydrochloric acid) for rust removal. Strong acids are dangerous, and there are many more effective chemicals. |
| − | Ospho | + | *[http://www.ospho.com/ Ospho] Manufacturer description: When applied to rusted surfaces, it resists/retards rust in chemical change on drying to a tough, hard surface ready for priming. |
*[http://rustbeeter.com/ Rustbeeter] Merchant description: A byproduct of the sugar refining process. Probably similar to molasses. Parts must be submerged. Parts soak in a bucket for usually under a week, but as long as several weeks. Food product. Dry powder that gets mixed with water. Non-acidic or caustic. After use, parts are cleaned with dish soap and water, dried, and coated. | *[http://rustbeeter.com/ Rustbeeter] Merchant description: A byproduct of the sugar refining process. Probably similar to molasses. Parts must be submerged. Parts soak in a bucket for usually under a week, but as long as several weeks. Food product. Dry powder that gets mixed with water. Non-acidic or caustic. After use, parts are cleaned with dish soap and water, dried, and coated. | ||
*[http://www.tinmantech.com/html/must_for_rust_remover_inhibi.php Must for Rust] Merchant description: removes rust and corrosion, non-caustic to skin, needs no neutralizing, primer goes right over it. $28/gallon. | *[http://www.tinmantech.com/html/must_for_rust_remover_inhibi.php Must for Rust] Merchant description: removes rust and corrosion, non-caustic to skin, needs no neutralizing, primer goes right over it. $28/gallon. | ||
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===Tips=== | ===Tips=== | ||
| − | *When using a wire wheel, don't sit in one spot for too long -- | + | *When using a wire wheel, don't sit in one spot for too long -- the localized heat from friction can warp sheet metal. |
==Methods== | ==Methods== | ||
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====Storing body panels==== | ====Storing body panels==== | ||
| − | Use epoxy primer ( | + | Use epoxy primer (aka "epoxy primer/sealer"), it won't allow rust. Not the same as regular primer. |
Wet-sand down to 400 grit, wash/dry, grind down rust to bare metal, apply body filler where needed, blow off, clean with prep-sol or similar cleaner, tape it up, and prime with epoxy primer. | Wet-sand down to 400 grit, wash/dry, grind down rust to bare metal, apply body filler where needed, blow off, clean with prep-sol or similar cleaner, tape it up, and prime with epoxy primer. | ||
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Have a machine shop polish the journals. | Have a machine shop polish the journals. | ||
| − | May require a regrind to the next correct bearing size prior to polishing depending on tolerances. | + | May require a regrind to the next correct bearing size prior to polishing depending on tolerances. |
| − | Using a decent regular flow of | + | Using a decent regular flow of CRC 5.56 or a PTFE type spray and an M3 grey scotchy (then try green scotchbrite if need) rubbed in direction of crank travel, localised to effected area. Mask off area with masking tape to prevent scratching unaffected areas if necessary. |
| − | Rust is tough, and large areas vigourously rubbed (mechanically or otherwise) may damage the finish of the journal. Initial contact needs to be with clean | + | Rust is tough, and large areas vigourously rubbed (mechanically or otherwise) may cause damage to the finish of the journal. Initial contact needs to be with clean CRC rinsed rag, keep the journal area clean and use a light touch, buffing in one direction until the initial rust colour no longer shows. |
| − | If sand paper is to be employed, try starting with 2000 grit( | + | If sand paper is to be employed, try starting with 2000 grit (no less than 1200 grit), change paper regularly, and keep the strokes light. You are only removing the outer scale, you are not resurfacing the journal just rubbing out rust. |
Phosphoric acid localised can help in any pits. | Phosphoric acid localised can help in any pits. | ||
| − | Acids on hardened steels can cause embrittlement so | + | Acids on hardened steels can cause embrittlement so dont leave it on long, only enough to blacken the rust. Afterwards switching to a microfibre rag with a product like Autosol, Blue Magic or even Brasso, you can polish out any minor scratches on the journal. Steel wool usually isn't recommended as it can scratch the journal finish, and it creates fine particles that must be throuoghly cleaned from the crank. If rust is more than 0.005" deep get it resurfaced. |
| + | Also- | ||
| − | + | * Very fine steel wool or scotchbrite pad, and light oil. Rub around the journals in the direction of rotation, not across. | |
| − | + | * Cut 600 grit wet or dry sandpaper into strips the width of the crank journals. Wrap it around the journal, and secure it with tape. Then, make a strap from leather, about one-half the width of the sandpaper strips. Use the strap on the paper in a shoeshine motion. Finish off with some light oil on the sandpaper. Do a few strokes first, then clean the paper, because the rust will clog the sandpaper. | |
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''(LP3 as rust inhibitor on crankshafts?)'' | ''(LP3 as rust inhibitor on crankshafts?)'' | ||
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Engine storage spray, or wipe down with [http://www.marvelmysteryoil.com/ Marvel Mystery Oil]. | Engine storage spray, or wipe down with [http://www.marvelmysteryoil.com/ Marvel Mystery Oil]. | ||
| − | Cylinder walls with flash rust: | + | Cylinder walls with flash rust: Marvel Mystery Oil, steel wool, etc. Pitted rusting will necessitate a rebuild. |
===How to de-rust gas tanks=== | ===How to de-rust gas tanks=== | ||
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