Rust
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=What causes rust?= | =What causes rust?= | ||
| − | + | ==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 electro-chemical 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. | ||
| − | + | 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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| + | Iron, with the chemical symbol of Fe, combines with oxygen, O, to form Fe<sub>2</sub>O<sub>3</sub>, the chemical formula for common reddish-brown rust. In its mineral form, Fe<sub>2</sub>O<sub>3</sub> is known as hematite. | ||
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| + | Rust is commonly referred to as ''iron oxide''. An oxide is a type of chemical compound that contains oxygen and other elements (like nitrous oxide, N<sub>2</sub>O). Oxides are typically formed when elements come into contact with air, through a process known as oxidation. Oxides are common, comprising most of the earth's crust. Elements can have multiple oxides. For example, there are sixteen known iron oxides. Thus, it's more accurate to say that rust is '''an''' iron oxide, rather than saying that rust '''is''' iron oxide. | ||
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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. | ||
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| + | 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. ''(Is this the same thing as blueing?)'' | ||
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| + | ===Why do older cars rust more than newer cars?=== | ||
| + | *Cars are more aggressively coated these days. Galvanizing (explain). | ||
| + | *Steel used in cars is of a higher quality these days. | ||
| + | *More salt is used on roads these days. | ||
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| + | =Rust assessment= | ||
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| + | ==The "best" way to handle rust== | ||
| + | The "best" way to do something often implies the existence of the "best" conditions in regard to skill, time, and money. | ||
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| + | For example, the "best" way to handle anything more than surface rust on body panels is to liberally cut out the rusted area, and weld in a patch panel. Ideally, any metal shaping and metal finishing should be done without the use of any body filler products whatsoever. Many people don't have the necessary skill to do this. | ||
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| + | The "best" way to handle surface rust on an entire body is to have it professionally dipped, often at a cost of over $1000. This amount of money may not be available for a specific project, or it may be impractical to invest it. | ||
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| + | If you take time to properly asses your own rust situation, you can choose a well-thought out solution that's "best" for you. | ||
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| + | ==Areas to assess== | ||
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| + | ===The rusted part or piece=== | ||
| + | *Can the part be removed? How large is it? Is it small enough to be soaked? | ||
| + | *What part is it? Is it a body panel? | ||
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| + | ===The rust itself=== | ||
| + | How bad is it? Exactly how to assess: | ||
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| + | *Jab rusty areas with a screwdriver, scratch awl, or icepick, and see if they go through. | ||
| + | *After cleaning rust off of floor pans, wait until it's dark, and put a trouble light under your car. Pinholes in the sheet metal will show up very well in such a situation. | ||
| + | *Rust coming through seams? (research this) | ||
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| + | ===Climate and operating environment=== | ||
| + | Do you live in a climate where water or salt will be present in the air? Is it a wintery climate where snow and/or salt will be present on the roads? Near the ocean? | ||
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| + | What environment will the part be operating in? Interior of car? Undercarriage? Submerged in oil? | ||
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| + | ===Skills=== | ||
| + | Most of the skills required for removing rust are commonplace. However, certain jobs may require welding, or metal shaping. | ||
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| + | ===Tools=== | ||
| + | Besides basic hand tools, do you have access to a DA sander? Media blaster? Spot blaster? Blast cabinet? Spray gun? | ||
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| + | ===Cost=== | ||
| + | How much money do you have to put into the rust removal? What's the value of the project? Are you doing it "for money or for love"? If you plan on selling the project, can you expect a reasonable return on your investment? | ||
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| + | ===Time=== | ||
| + | How much time can you put into the project? Both work time, and wait time. Do you have the time necessary to eliminate surface rust from a body by hand? Do you have time to drop a part into a bucket, and wait a few weeks while it soaks? | ||
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| + | ===Overall vehicle plan=== | ||
| + | What's your overall plan for the vehicle with the rusted part or piece? What kind of abuse is it going to take, and how important are looks? Will it be a daily driver? Are you going to show it? | ||
=Rust removal, treatment, and prevention= | =Rust removal, treatment, and prevention= | ||
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