Rust

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A rusted battery tray alongside a new one.

Contents

[edit] What causes rust?

[edit] 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.

Iron, with the chemical symbol of Fe, combines with oxygen, O, to form Fe2O3, the chemical formula for common reddish-brown rust. In its mineral form, Fe2O3 is known as hematite.

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, N2O). 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.

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 Fe2O3, 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 Fe3O4, 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, Fe2O3. 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?)

[edit] 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.

[edit] Rust assessment

[edit] 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.

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.

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.

If you take time to properly assess your own rust situation, you can choose a well thought-out solution that's "best" for you.

[edit] Areas to assess

[edit] 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?

[edit] The rust itself

How bad is it? Exactly how to assess:

  • 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)

[edit] 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?

What environment will the part be operating in? Interior of car? Undercarriage? Submerged in oil?

[edit] Skills

Most of the skills required for removing rust are commonplace. However, certain jobs may require welding, or metal shaping.

[edit] Tools

Besides basic hand tools, do you have access to a DA sander? Media blaster? Spot blaster? Blast cabinet? Spray gun?

[edit] 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?

[edit] 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?

[edit] 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?

[edit] Rust removal, treatment, and prevention

[edit] Chemicals and finish products

[edit] Understanding "magic formula" marketing

The market for rust removal, conversion, and encapsulation products is rife with far-fetched claims of "secret formula" rust solutions.

Realistically, it's not very difficult for one company to chemically analyze another company's "secret formula", and produce an identical (or extremely similar) product. Many of the various rust removal and encapsulation products are, more or less, the same. A lot of it boils down to marketing, and the situation is only exacerbated by the fact that it's difficult to make a thorough assessment of a rust treatment product. Properly assessing a rust treatment solution would likely involve waiting several years, and then removing any outer layers of finish so that any existing underlying rust could be examined.

The uneducated consumer will likely recoil at the abundance of "magic" formulas for treating rust, and revert to selecting a safe, well-known, name-brand product line. This is a reasonable solution for many, but the name-brand rust treatment products tend to be rather expensive, especially in consideration of the fact that they are often comprised of inexpensive, common chemicals.

Someone who has achieved good results with a certain combination of rust treatment products will often stay loyal to their method, without exploring other potential options that may indeed provide better results at a lower cost.

[edit] Miscellaneous (need to be sorted)

[edit] Rust removers and "converters"

After using an acid to remove rust, flush the surface with water and baking soda (confirm or expand on this).

When converting/neutralizing rust:

  1. Get everything off first that you can by sanding and wire brushing (wire brushing will get into the pits better).
  2. A rust converter/neutralizer containing tannic acid, phospheric acid or another type of acid should be used
  3. Be careful of getting this stuff on your concrete floor as it will bubble and decompose it.
  4. Follow the instructions on the bottle when you are done there should be a fine coating on the metal which will help prevent further rust from developing.
  5. This stuff is hard on paintbrushes (eats away the brisles) and you must be very careful of your eyes. Also it will ruin paint, so, again, use caution.

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. It's too dangerous, and there are many more effective chemicals. Ospho

  • 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 dishsoap and water, dried, and coated.
  • Must for Rust Merchant description: removes rust and corrosion, non-caustic to skin, needs no neutralizing, primer goes right over it. $28/gallon.
  • Eastwood Rust Converter Merchant description: 2-part mix, adheres to bare or rusty steel, and can be topcoated with most coatings. 1 gallon each of the 2-part mix is $125.
  • Rust Cure Merchant description: phosphoric acid-based. leaves a thin film that bonds well with most primers and paints. for pricing, need to see this page: http://rustcure.bizland.com/xwheretobuy.html .
  • Oxisolv Rust Remover Merchant description: dissolves rust and leaves behind a zinc phosphate coating. Spray/brush/dip. Non-toxic, non-flammable, and re-usable. Must be cleaned off before priming.
  • Eastwood Rust Dissolver Merchant description: acid free rust remover, leaves surface ready to paint, plate, or powder coat. Suitable for engine parts, and harmless to copper, brass, aluminum, solder, lead, plastic, rubber, seals, wood or vinyl. Surface must remain wet for product to work. $40/gallon.
  • Rust-Mort Merchant's description: "Converts rust to a black or grayish, hard, insoluble, protective coating".
  • SEM Rust-Seal Manufacturer description: "Transforms rust leaving a tough, permanent, black protective coating. RUST-SEAL can be left exposed or may be topcoated with enamels, lacquers or urethanes."

(Make sure that none of the above count as "encapsulators". Also, what about the converters that leave a "protective film" on the metal. They say that they don't need neutralization, and they don't need to be washed off. Is this as good as cleaning to bare metal, and then hitting with epoxy primer?)

  • Vinegar
  • Muriatic acid (not for use on body panels, as it causes hydrogen embrittlement)
  • Toilet cleaner (?)
  • Cola (yes, contains phosphoric acid)
  • Phosphoric acid: leaves behind a coating of iron phosphate
  • Naval jelly (gelled phosphoric acid)
  • Mag wheel cleaner (?)
  • Molasses (a 1:10 solution of molasses to water can be used for soaking rusty parts, although it loses its strength after several months)
  • Powdered household cleaning products such as Comet or Ajax

[edit] Rust encapsulators

Main article: Rust encapsulators

Rust encapsulators work by sealing off existing rust, denying it the oxygen it needs to grow.

The use of rust encapsulators in hotrodding is controversial. Hotrodders typically divide into 3 distinct camps over the use of rust encapsulation products on vehicles:

  1. Won't use rust encapsulation products at all.
  2. Will use rust encapsulation products, but not on body panels.
  3. Will use rust encapsulation products on a variety of parts, including body panels.

[edit] Rust preventive oils and waxes

  • Cosmoline . "Cosmoline" is a trade name for a generic rust preventative which conforms to US military specification MIL-C-11796C. It's a soft, brushable grease that's commonly used for preserving and storing firearms. "Rated to protect polished steel panels from rust for one year in open shed storage, and 30 days, minimum, in a humidity cabinet." $30/gallon
  • Boeshield T-9 "Designed to penetrate metal pores and dissolve minor corrosion, then leave a resilient waxy coating that lasts for many months." $100/gallon
  • Eastwood Heavy-Duty Anti-Rust. Merchant's description: spray-on brown wax film which forms an air and water-tight barrier. won't crack, flake, or peel. used for inside door panels, or to protect bare metal parts during storage. $15/quart
  • Oxisolv rust inhibitor long term -- Merchant description: displaces water on metal parts to prevent rust. environmentally safe, bio-degradable, protects steel. Apply by spraying thoroughly, or dipping.
  • SEM internal panel coating Manufacturer description: "provides corrosion protection to inner body panels and other metal parts"
  • 3M Rust Fighter application wand
  • 3M Rust Fighter
  • Brownpolymer rust inhibitor long term -- Merchant description: displaces water on metal parts to prevent rust. environmentally Safe,It's a Cleaner,It's a Polish,It's a Lube, It's a Grease,It's a Protective Coating,Multi Use Polymer Substance
  • You can make your own basic rust protection coating from 1 part anhydrous lanolin (available from a pharmacy), and 5 parts paint thinner.
  • For machine tools, this is recommended: http://www.clclubricants.com/waylubes.htm .
  • Use something that releases rust-inhibiting vapor. Rust-blox vapor tabs, vpi paper, permatex in-charge corrosion inhibitor.

[edit] Epoxy primer

Main article: Epoxy primer.

Epoxy primer/sealer is a non-porous finish that is typically recommended as the first basecoat over bare steel. Various epoxy primers can also be applied over fiberglass, plastic, or the black iron phosphate coating that remains after "converting" rust.

Epoxy primer is a two-part mix, with a hardener that has to be added before spraying. Body fillers and high-build primers can be used on top of epoxy primer.

[edit] Seam sealers

Seam sealers are used to seal roof channels, drip rails, trunk seams, door seams, and other body seams. They can be either one or two-part, and are typically applied over primer, sometimes with the use of a specially-designed caulking gun or spray gun.

[edit] See also

"Basics of Basics": Seam Sealers (by Brian Martin)

[edit] Metal washes, wax and grease removers

  • Eastwood Metal Wash. Merchant's description: dry compound that is mixed with water. removes grease and oils from bare metal, and leaves behind corrosion inhibitors that prevent flash rusting and promote paint adhesion. $11 for enough dry mix to make 7 quarts.
  • Metalprep 79 Manufacturer's description: phosphoric acid-based cleaner. leaves surface chemically clean and corrosion free. thoroughly rinse with water when done. brush/spray/dip
  • Is DuPont's "Quick-Prep" equivalent to Metalprep?

Read this thread thoroughly: http://www.hotrodders.com/forum/what-else-wax-grease-remover-besides-mineral-spirits-51150.html

The following are not to be used as metal cleaners: lacquer thinner, acetone, reducers. Use the product within the recommendations of your product system. Cleaners typically vary as to strength, and time they take to evaporate.

Use clean, purpose-designed paint rags for cleaning with cleaners.

[edit] Weld-through primer

Weld-through primer zinc-rich coating that conducts current from a welder, and doesn't burn off when welding. It can provide protection on lap welds and inner weld seams.Weld-through primer is often applied to the mating areas when welding body panels.

  • 3M
  • U-Pol

[edit] Panel adhesives

Used to adhere body panels, as an alternative to welding. Need more information on these.

[edit] Tools

  • Shop vac
  • Putty knife
  • Metal brush
  • Sand paper. 36 grit to 220 grit.
  • Wire wheel on drill. When the wire bristles start to bend one way, reverse the drill and work in the other direction for a while.
  • Wire wheel on grinder, or, these discs are considered to be superior to wire wheels: 3M clean & strip disc, or 3M bristle disc, or Surface Conditioning Disc.
  • Scotch-brite pads
  • Steel toothbrush
  • Media blaster
  • Blasting cabinet
  • Spot blaster
  • Welder
  • Steel wool

[edit] Tips

  • When using a wire wheel, don't sit in one spot for too long -- it will warp the metal.

[edit] Methods

[edit] Body panel rust removal

Ideally, only surface rust on body panels is "treated". Anything more than that would mean that the affected area would be cut out, and replaced with fresh metal.

[edit] Removing surface rust from body panels

First, remove all the heavy surface rust with a DA sander and 80-180 grit paper. To remove surface rust, use naval jelly (jelled phosphoric acid) and steel wool.

  1. Work in small areas, not larger than a square foot. Wear rubber gloves, and scrub with naval jelly and steel wool.
  2. Apply jelly with 000 steel wool, rub it in, and allow it to set for a couple of minutes. Don't let it dry. Keep it wet, using a squirt bottle. For inclines, you can also soak some fabric in water, and lay it on the naval jelly.
  3. Rub again with steel wool. Repeat a few times.
  4. When finished, wipe off the excess naval jelly with a paper towel, squirt on warm soapy water, and dry thoroughly.
  5. Wipe down with lacquer thinner.
  6. Sand with 180 grit.
  7. Use wax and grease remover, and then spray with epoxy primer.
  8. From there, you can apply body filler (the epoxy may need to be scuffed, read instructions).
  9. When the filler work is done, scuff with a red scotch-brite pad.
  10. Then, apply two more coats of epoxy, followed by high-build primer.

[edit] Cutting out rust

First, make a tape template. Tape off the area that's going to be cut off, leaving a healthy border of good metal. Transfer the tape template to the patch panel, in one piece. Cut out the templated piece from the patch panel. Then, screw the cut-out piece to the car as a temporary guide. From there, rough-shape the patched piece. Cut some slits if necessary, and hammer. Then, make the cut on the body panel, with the patch still screwed to the car. Then, unscrew the panel from the car, and hammer-form it on a bench, anvil, etc. Finally, butt-weld it back onto the car. Weld, with lots of spread-out spot welds (wait for them to cool), so the panel doesn't warp. Then, grind down the welds. Treat with rust protection, then body filler, primer, etc.


A quarter panel rust fix demonstrating the above is illustrated here: http://www.a2zautoforums.com/showthread.php?t=700


[edit] Treating light body rust (from storing panels) prior to epoxy

Sand with 80 grit, wash with wax and grease remover. Use waterborne wax and grease remover, instead of solvent-borne (research exactly what that means), let set 15-30 minutes. Dry with a blower and a tack rag. Spray epoxy.

[edit] Getting the entire vehicle body dipped

(Need more info on Redi-Strip. What chemical do they use? What's the cost? Can a hobbyist acquire and use the same chemical that Redi-Strip uses? When the body is returned to you, is it truly completely clean, or does it have to be cleaned to get all of the chemical removed from nooks and crannies, etc.?)

[edit] Quick fix for exposed areas (dents, etc.)

If a dent causes an area of bare metal to be exposed. To "hold" it so it won't rust until a paint job is ready to be done: gently bump out the dent, sand, rattle can primer, rattle can sealer.

[edit] Do both sides of a panel have to be treated with rust converter/encapsulator?

Explain this.

[edit] Removing pitted rust in body panels

See: pitted rust.

[edit] Fixing rust holes in body panels

See: pitted rust.

[edit] Storing body panels

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.

[edit] Removing rust in seams

A spot blaster is useful.

To do it right, you will generally need to pull the seam apart, remove the rust, and then hit it with a rust conversion product. However, sometimes you can open up the layers slightly with a hammer and putty knife used between the spotwelds. Bend the flange open, media blast into the seam, clean, prime with epoxy primer, brush in urethane seam sealer, and close the seam back up. If the seam is not accessible, flood it with a penetrating cavity wax, like 3M's Rustfighter.

[edit] Accessing rust between interior panels

Pressure washer with pencil tip can knock everything loose out.

Drill small holes, get a spray wand with a 360-degree head. Then, when done, weld the holes shut.

Turn panels around to slosh rust remover around. Blow compressed air inside the panel.

Cut hole in panel? Spray rust killer with garden sprayer?

A mirror can be used to check areas for rust.

Don't spray expanding foam. It absorbs water, and will cause more rust. It can also expand and cause the panels to push out.

[edit] How to treat rusty drip-rails?

  1. blast
  2. wash with wax and grease remover
  3. spray with 2 coats of epoxy
  4. spray with seam sealer

[edit] Plasma spray welding

With plasma spray welding, metal wire is converted to sprayable form, and used to repair rust holes, fill panel joints, and blend patch panels. One example is the machine sold by Rustbusters.

[edit] Rusted window channels

(Difficult to fabricate, need more info on this.)

[edit] Vinyl tops

Rust is common in vinyl tops. The vinyl gets porous after a few years, and lets in moisture.

(How to prevent?)

[edit] Leaf spring rust

Remove rust, then, ideally, paint them separately. Re-assemble with teflon strips.

[edit] Preventing rust at chassis to ground connection

Silicone dielectric grease, electrical bonding paste; spray well with clear lacquer after bonding the connection.

[edit] Cleaning light surface rust off crankshaft

Have a machine shop do it, or:

  1. Very fine steel wool or scotchbrite pad, and light oil. Rub around the journals in the direction of rotation, not across.

OR

  1. Cut 600 grip 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.

(LP3 as rust inhibitor on crankshafts?)

[edit] Electrolysis

Advantages: self-limiting (can't remove too much), safe (low electrical current), won't harm good metal, not an acid (less dangerous, and no risk of hydrogen embrittlement)

Need: a plastic tub, iron electrode, water and washing soda (sodium carbonate), and a batter charger. About 1 tablespoon of soda per gallon of water. Can't find washing soda, then lye will work. Wear eye protection and protect skin too. Connect the electrode to the positive battery terminal. Connect the rusted object to the negative terminal. Submerge the object. Make sure the contact is good (may need to clean off some of the rust from the rusty part). Typically takes a few hours, but can take up to overnight. Rinse or scrub with brush to remove final rust debris. May need to re-treat. Oil, wax, or prime soon after. Surface of rusted metals is black after treatment.

Be creative to clean oddly-shaped objects:

  • plastic PVC pipes
  • large 2x4 wood boxes lined with plastic sheeting
  • suspend an electrode in a cavity
  • use a sponge soaked in the electrolyte solution, with a backing electrode, for objects that can't be submerged.

The powder used is a mild alkali.

[edit] Resources

[edit] How to remove rust from chrome

  • Mag wheel polish, or Turtle Wax Chrome Polish.
  • Fine steel wool, scotch-brite pads, crumpled-up pieces of aluminum foil.

[edit] Preventing engine rust

Engine storage spray, or wipe down with Marvel Mystery Oil.

Cylinder walls with flash rust: marvel mystery oil, steel wool, etc. Pitted rusting will necessitate a rebuild.

[edit] How to de-rust gas tanks

Put a handful of nuts and bolts in, chain, chainsaw blade, etc., and shake it around a bit to knock out the loose stuff. Not too aggressive -- you'll dent the tank. Then, clean with phosphoric acid. Pour it in, let it sit for up to an hour, then flush with water and baking soda to neutralize. Or, Eastwood has a kit for this: an acid to clean it, and then something to coat it with. However, some people say that the coating can clog up the fuel filter, or trash your OEM sending unit. The best way to do it is to take it out and get it re-tinned.

[edit] How to clean engine water jackets or radiator of rust

Flush with CLR, Kool Klean (can't find). Manufacturers of CLR say that it shouldn't be used in a radiator: http://www.jelmar.com/CLRbasic.asp .

When building an engine, to prevent rust: when done washing it and blowing it dry, oil it down, and store it in a plastic bag -- sealed (confirm this).

[edit] "Oiling" your car

In climates that are more prone to rust, cars are sometimes "oiled". Rocker panels, doors, and other body passages are drilled and sprayed inside with oil, used oil, or gelled oil substances. Entire frame and suspension are also oiled. Can be done yearly in very rust-prone climates.

Historically, this procedure has been used before driving the car down a dirt road. The dirt sticks to the oil on the underside of the vehicle, providing an effective sealing layer. Consider how, when removing a dirty, oily gasket, the metal beneath it is clean. Same concept.

Now, this might be done with an application-specific undercarriage wax or oil.

[edit] Preventing MIG wire rust

Store in a bag with some dessicant packets. Here's a list of dessicants: List of dessicants. Also, can use small old refrigerator with 100 watt bulb inside, for storing rods and wires. Stays about 100 degrees. Small fan inside too.

[edit] Underside rust removal

Best not to do this as overhead work. Tilt the car on a rotisserie, or raise it significantly overhead.

Another option is to keep the car low to the ground, and, with plastic sheeting and duct tape, seal the area between car and floor. Leave the rear area of the plastic "tent" open for access. At the front of the "tent", affix a shop vac hose (exhaust). Blast.

[edit] Rustproofing brake rotors

Zinc dip, also Eastwood has some solutions? Research this.

[edit] Axle tube rust

When rebuilding a rear end, the rust can be cleaned out with naval jelly/shoving rags down it with a broomstick.

[edit] Cleaning hand tools

Tumble in a cement mixer with oil and sand. Or, soak in a bucket with parts cleaner or paint thinner.

[edit] Rust prevention on tools

Keep tools in a wooden toolbox. Also, use a shop dehumidifier. Avoid dust on your tools, as it can attract moisture, and thus, rust.

[edit] Electronic rust inhibition

(This is known as cathodic protection. Research this. And: sacrificial anode and galvanic anode.)

[edit] Frame rust

Sandblasting or dipping is best. Then, stripping wheel or wire wheel is next-best. Can be professionally sandblasted and powder-coated for ~$250 at a good price.

Patching is usually not worthwhile, unless it's a special or valuable frame. Too easy to replace, and too much potential structural damage. Has to be done perfectly. Can be replaced with steel of the same gauge as the original frame, and welded in to place.

Where is the rust on the frame? In a critical stress area? How bad is it?

For minor surface rusting, with mostly metal showing through, it's OK to just powder-coat it.

OR:

  1. blast/wire wheel
  2. phosphoric acid
  3. clean off acid with thinner
  4. etching primer
  5. epoxy primer

[edit] Cleaning the inside of a boxed, open-ended frame

Blow out all the dirt, etc. Then, attach a strong towel to some strong cord. Soak the towel with rust treatment chemical, and pull it through the frame.

[edit] Media blasting rust

See: Media blasting.

  • Sand is not recommended for media blasting panels. It acts like little hammers, warping panels with compressive forces (analagous to hail). It can be done, but extreme caution must be used. Sand also dulls as it is used, which reduces its cutting efficiency with each reuse.
  • Use softer media (list examples):
    • 55 grit silica-based media
    • Sugar sand is finer and less-damaging than regular sand.
  • Can sandblasting "increase" rust? Or, if the rust is removed and the metal is sealed, shouldn't it be eliminated? Some thoughts on this are:
    • Although sandblasting may appear to have removed all the rust to the naked eye, it hasn't really done so.
    • It's caused by water in the air compressor line, as sand will harbor some moisture. Also, compressed air contains moisture. And, sand has salt in it. A moisture trap in the line should solve the problem with the water in the air line.
    • Sand by hand after sandblasting, to eliminate this issue.
  • Many panels have seams, hems, and bends that are inaccessible by blasting, and can hold moisture and rust. A spot blaster is recommended.
  • One option is to use chemical paint stripper, then use a sandblaster to lightly "dust" the remaining rust.
  • Media blasting can remove good metal from body panels too. Also, used media can have metal particles left in the media.
  • Soda blasting can remove light rust, and won't warp panels. However, when soda blasting body panels, the resultant film can negatively affect finish adhesion. For more details, see: Soda blasting.

[edit] Miscellaneous

[edit] Flooded vehicles

Flooded vehicles can be very difficult to handle, as there can be rust in any and all places. They are best avoided, unless it's the car that you really want.

[edit] What's galvanization?

(needs confirmation)

"Galvanizing" typically refers to hot-dip galvanizing, a process by which iron or steel is coated with a thin layer of zinc, by dipping it in a molten bath of zinc. Galvanized steel can be welded. It's been used for more than 150 years.

Zinc oxidizes when exposed to air, forming zinc oxide, which then reacts with water molecules in the air to form zinc hydroxide, which then reacts with carbon dioxide in the air to form zinc carbonate. Zinc carbonate (the final "galvanizing" layer), is a thin but very tough protective layer. It also acts as a "sacrificial anode". It will corrode before the steel it is protecting.

Many modern automotive body panels are galvanized.

You can buy cold galvanizing spray. (list examples here)

[edit] Hydrogen embrittlement

All acids contribute hydrogen to metal. This causes hydrogen embrittlement, which weakens the metal. Untrue: you can "bake" the hydrogen out at 400 degrees F, after exposing a metal to acid.

[edit] Fiberglass resin patches

One technique that has been recommended is to grind/clean the rust, tape the underside of the panel to be patched, and then fill the holes with fiberglass resin, then paint and undercoat. This trick is not really a good idea -- when the body flexes, there will be cracks in the fiberglass pieces. Metal also expands at different rates than fiberglass, causing cracks to form, allowing more rust to form in these cracks.

[edit] Do metal etches leave coating?

Follow up on metal etches like DuPont's Metal Etch or POR's Metal Ready leaving a phosphoric acid coating on the metal that will prevent flash rusting while storing.

[edit] How to remove rust protection

How to remove old rust protection finishes? Or undercoating?

  • Wire wheel
  • Brake cleaner
  • Kerosene
  • Heat gun
  • EZ-Off oven cleaner
  • Mineral spirits
  • Freeze with dry ice, then chisel out
  • Wallpaper steamer

[edit] What about riveting in patch panels?

Very low-end solution, like fiberglass patching metal. Panel adhesives are a better choice when you can't weld.

[edit] Resource dump

Drop links in here if they're relevant to this article. They'll be reviewed, incorporated, and referenced.

[edit] Related resources

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CaacdElbas, Chevythunder, Crosley, Eloc431962, Jon, M&M CUSTOM, Metzijndrie, Powerrodsmike

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