Powder Coating: Mechanical Parts Cleaning Guide

This type of parts cleaning includes both manual and motorized cleaning methods; no chemicals are involved. In addition to wire and nylon brushes, you want to have a couple of scrapers on hand to remove caked grime. A good putty knife works well for surfaces where scratches don’t matter. Otherwise consider a plastic spatula.

 


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Another great cleaning tool is a big pack of common kitchen Scotch-Brite or similar pads. You can use them and throw them away when they get dirty. They also make good filter elements if your bench-top parts washer has a fluid pump. You can use kitchen scouring powder with the pads for very good results.

 

If chemical cleaners don’t get the grunge off your parts, you have to scrape it off using whatever tool works. Sanding wheels, wire brushes, and scrapers are all part of your arsenal.

If chemical cleaners don’t get the grunge off your parts, you have to scrape it off using whatever tool works. Sanding wheels, wire brushes, and scrapers are all part of your arsenal.

 

For long bolts, you should have a bench grinder outfitted with a fine-steel wire wheel or a soft-bristle wheel to remove rust and accumulated gunk. For a complete job, a buffing wheel is a nice addition. You can use some jeweler’s rouge to polish many parts to a high shine.

For delicate or intricate work, you may want to spend some time with a set of dental picks, working the grease or crud out of brand-name stampings or other indentations. The same technique is often used on the nooks and crannies of brackets and castings. With any abrasive blasting, dust is an issue. There’s always a little bit of material left in gaps, spaces, and box sections. Do your best to clean that out with a shop vacuum, compressed air blower, and the time-honored method of turning the part over and shaking it. But don’t be surprised if you don’t get it all.

 

Brushes

A basic handheld wire brush is an important tool in your cleaning arsenal. Be sure to have a selection of them with plastic, brass, or steel bristles. Use these brushes in combination with a solvent or detergent parts washer to really get in and scrub your parts. The job takes longer with a handheld brush, but you can work in a careful and precise manner.

 

Basic scrubbing brushes are handy. Get a variety of brushes with bristles of brass, plastic, and steel wire.

Basic scrubbing brushes are handy. Get a variety of brushes with bristles of brass, plastic, and steel wire.

 

For fine work, recycle your old tooth-brushes. They come in very handy and if they get mucky you can just throw them away.

For fine work, recycle your old tooth-brushes. They come in very handy and if they get mucky you can just throw them away.

Here’s another tip: Keep your old used toothbrushes in your shop for super-fine detail cleaning work.

 

Wire Wheels

Wire wheels come in all sizes and grades of wire. Some have straight bristles, while others have twisted or knotted wire for extra toughness. You can attach a wire wheel to a power drill for a low-speed and gentle tool, or put one on a bench grinder or auto body grinder for more intensive work.

 

Any hardware or tool store should have a wide selection of wire wheels for your bench grinder. Many shops use two or more bench grinders with wire wheels of varying stiffness (different wire grades) for different purposes.

Any hardware or tool store should have a wide selection of wire wheels for your bench grinder. Many shops use two or more bench grinders with wire wheels of varying stiffness (different wire grades) for different purposes.

 

Always be aware of the danger of a wire wheel. They throw off wires constantly, and your eyes are always in the line of fi re. Keep a pair of safety glasses next to every wire wheel. And use them!

 

Grinders

Sometimes, to clean a part you need a grinder. Depending on the project, you might choose an auto body grinder, a belt grinder, or a bench grinder. Remember to always be careful and take it slow: Haste is not your friend when you’re using a grinder.

Auto Body Grinders

Auto body grinders, also known as angle grinders, are very versatile tools for removing thick grunge and rust. In addition to standard abrasive grinding wheels, you can use a variety of other attachments. These include fine and coarse wire wheels, cup-shaped wire wheels, sanding discs with sandpaper or coarse scrubbing material, and flap discs.

Of all these, the wire cup wheel is generally the best for simply removing large amounts of material from an iron or steel surface without damaging the underlying metal. Coarse scrubbing discs also work well while protecting the metal underneath the paint or grunge. Plain bristle wire wheels are good for light-duty removal, such as spray paint, and knotted wire wheels work well for tougher jobs.

 

A basic auto body grinder doesn’t cost much, but get a good one. You can use flat wire wheels, cup wire wheels, grinding wheels, and sandpaper flap wheels on these versatile tools.

A basic auto body grinder doesn’t cost much, but get a good one. You can use flat wire wheels, cup wire wheels, grinding wheels, and sandpaper flap wheels on these versatile tools.

 

A cup wire wheel has multiple twisted wire brushes. These are fantastic for removing thick coatings of grunge, paint, and anything else. This tool also removes the flesh from your bones nearly instantly, so be careful when using it.

A cup wire wheel has multiple twisted wire brushes. These are fantastic for removing thick coatings of grunge, paint, and anything else. This tool also removes the flesh from your bones nearly instantly, so be careful when using it.

 

Flap discs are made of overlapping sheets of extra-tough sandpaper, and these are a great alternative to hard abrasive discs. In general, if you’re careful and don’t press too hard, a flap disc removes rust and paint without gouging or removing too much metal underneath.

If you have metal-filler restoration products for filling grinding gouges, you can go ahead and use an abrasive grinding wheel with your auto body grinder to really dig in and take the part down to its good metal.

 

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Belt Grinders

Benchtop belt grinders have an important place in rust removal but not so much with grunge or paint. These grinders typically have flat faces and at least one curved surface to remove material quite quickly. Use this type of grinder to strip rust or thick, hard coatings, such as old powder coating.

 

This professional-grade belt grinder is worth the investment if you plan to do much fabrication and metalwork. Cheap belt grinders take forever to get anything done.

This professional-grade belt grinder is worth the investment if you plan to do much fabrication and metalwork. Cheap belt grinders take forever to get anything done.

 

Belts come in a variety of grits, and you should choose the finest grit that works for your purpose. The cleaning work takes a little longer, but the process removes less metal from the part.

Bench Grinders

The best use for a bench grinder as a parts cleaner is with a wire wheel. Put a soft wire wheel on one side, and a stiffer wheel on the other. If you have more than one bench grinder, consider adding a buffing wheel. Wire wheels on a bench grinder are ideal for removing rust from small parts; they’re much better than a drill-mounted or handheld wire brush.

 

The bench grinder is a tool no shop should be without. Buy a powerful one with at least one wire brush wheel. Chances are good you’ll buy a second one to go with it.

The bench grinder is a tool no shop should be without. Buy a powerful one with at least one wire brush wheel. Chances are good you’ll buy a second one to go with it.

 

Sanding

You can do a good job of cleaning parts with sandpaper or a power sander. Each method has its benefits, depending on the project at hand.

 

A palm sander is a good compromise between hand tools and power tools. This one allows you to poke holes in the sandpaper so the tool can vacuum out the dust. A small bag attaches to the tool for dust collection.

A palm sander is a good compromise between hand tools and power tools. This one allows you to poke holes in the sandpaper so the tool can vacuum out the dust. A small bag attaches to the tool for dust collection.

 

Hand Sanding

With sandpaper, you want to use a sanding block for flat or smoothly curved surfaces. Use a staple gun to attach sandpaper to a piece of 2 x 4 for the perfect sanding block. For irregular surfaces, your hand may work better, but you have to be careful.

Auto body workers use the following technique for getting even sanding results: Place a piece of sandpaper over the part and press down with your flat hand. If you move your hand forward and back in line with your fingers, you create grooves in the metal where your fingers put pressure on the sandpaper. Instead, always move the sandpaper in a side-to-side motion to keep even pressure on all points.

Power Sanders

A variety of power sanders create the best solution for prepping parts. Palm sanders are used for finish work and fill the same function as a sanding block. Orbital sanders are large and flat, which helps avoid digging in too much in one place. Disc sanders are tricky to use because it’s easy to dig a big curved groove into your part. Be sure to keep the sander flat against the part, and practice a lot before disc-sanding a vital part. Handheld belt sanders have the same issue; they make it easy to cut a groove into the part.

 

Media Blasting

Media blasting is also called sand blasting because sand is the most common media. But you can also use ground nutshells, baking soda, glass beads, plastic beads, or other materials. The basic process is simple: The media is blown at the part and hits it hard enough to remove paint, grimy build up, or even materials (such as body filler or lead) that have been used to smooth gaps and holes in the material.

Never use media blasting on items made from thin, stamped sheet metal. The blasting action stretches and warps the metal. Save this treatment for rigid parts such as wheels.

You can perform effective media blasting in your home workshop. A shop-size abrasive blast cabinet, or bead blaster, is a metal box that sits on your workbench. Also available are small plastic-bodied cabinets and large benchtop or freestanding metal cabinets. These cabinets have glass windows so you can see inside, and integrated rubber gloves so you can handle the parts without blasting your hands.

 

This wheel from a vintage Mini Cooper was the main project for a media blaster outfitted with glass beads. The beads are small (like sand grains); this wheel has some dirt, but mainly a couple coats of old spray paint on it. I could have used some stripper, but this is a good blasting test.

This wheel from a vintage Mini Cooper was the main project for a media blaster outfitted with glass beads. The beads are small (like sand grains); this wheel has some dirt, but mainly a couple coats of old spray paint on it. I could have used some stripper, but this is a good blasting test.

 

The blasting work was slow going with a Harbor Freight blast cabinet, but the results were great. It just takes some patience and a big compressor to run the required amount of air through the system.

The blasting work was slow going with a Harbor Freight blast cabinet, but the results were great. It just takes some patience and a big compressor to run the required amount of air through the system.

 

The wheel was perfectly clean when I was done, with a satin finish from being bombarded with all those beads for about an hour.

The wheel was perfectly clean when I was done, with a satin finish from being bombarded with all those beads for about an hour.

 

Once again, this project proved that the most important factor for a good powder coating finish is doing a good job on the prep work. This wheel will carry that shiny blue coating for decades, and look just as good as it did when I took it out of the oven.

Once again, this project proved that the most important factor for a good powder coating finish is doing a good job on the prep work. This wheel will carry that shiny blue coating for decades, and look just as good as it did when I took it out of the oven.

 

You can purchase a cabinet for less than $150 but there are related expenses: You need an air compressor that can keep up with the demands of the blaster. An inadequate compressor means that you need to pause every time the pressure falls below your working needs. Also, there is the expense of the abrasive compound, gloves, and window glass, all of which need replacing over time.

Most cabinets come without the air hose and fittings necessary to connect it to the compressor. Also be prepared to visit a hardware store for a pressure regulator. In addition, sometimes too much pressure prevents the media blaster from vacuuming up the media; if you’re not getting good results, reduce the pressure a bit.

Media blasting removes grime, paint, and rust very nicely, but you should always start with parts that are as clean as possible. Take the time to scrape and brush the worst of the grunge off the parts before you blast or you end up replacing the abrasive compound frequently.

 

The best abrasive material is glass bead. This is a clean, fine powder that is gentle on parts. Using dirty or cheap abrasive compound can embed ferrous particles into the surface of aluminum or stainless steel, which can rust and cause problems.

Commercial Media Blasting

Commercial media blasting is useful primarily for large items that you are not likely to powder coat at home. It is also popular for items that you may be coating at home, such as wheels and suspension components.

If you do use a commercial blaster, always insist that they use walnut shells, plastic beads, or soda on lightweight items. These lighter media types remove surface rust, but not deep rust. If you have deeply rusted project parts, you may need to pursue more extensive restoration on the parts before you continue with the powder coating process.

The best news is that commercial media blasting on small items is not expensive, and you may find that it’s a great way to reduce the time it takes you to prepare your projects. Plus, commercial blasters almost always obtain better results.

 

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Media Blasting Cabinets

An air-powered media blasting cabinet is a useful tool. If you have to take paint off metal, there’s nothing like a blast cabinet. You can purchase a freestanding or a benchtop version at a tool supply store.

Freestanding cabinets accept items up to the size of an exhaust header or loose wheel. Bench-mounted blast cabinets are usually made from injection-molded plastic. They are great units because they are portable and keep the blast media in the cabinet effectively.

Freestanding and some bench-top blast cabinets usually have to be assembled from parts made of stamped sheet metal. Some foam-rubber gaskets are included, but they don’t work well so these cabinets leak tiny glass-bead dust everywhere. You can get around this with a tube or two of clear silicone RTV. Use the RTV to seal each joint as you assemble the cabinet.

You also want to add a filter to the outlet vent of any blast cabinet. You’re putting a lot of pressurized air into the cabinet, and as it vents, the air tends to carry dust and abrasive with it. A filter keeps the abrasive compound inside the cabinet, but be sure to check and clean it frequently.

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This blast cabinet is big enough to take valve covers, exhaust manifolds, and smaller wheels up to about 15 inches in diameter. This cabinet, with everything you need, can be purchased from Harbor Freight tools.

This blast cabinet is big enough to take valve covers, exhaust manifolds, and smaller wheels up to about 15 inches in diameter. This cabinet, with everything you need, can be purchased from Harbor Freight tools.

 

You can also prevent a big mess by installing an evacuation blower. A sawdust evacuation system from a woodshop, for example, can be plumbed into the blower vent. Then direct the exhaust out of your shop. Otherwise, no matter how careful you are, you end up with a dusting of abrasive glass beads all around your blast cabinet.

When it comes to blasting, less is often more. Don’t put more abrasive material in your cabinet than absolutely necessary to ensure a steady supply, and use the lowest possible air pressure from your compressor. If you use too much pressure or too much abrasive, the material does not move through the blast gun.

Also, be aware that the hoses and fittings that come with less expensive cabinets are prone to kink and collapse. You may need to find some reinforced tubing at a home supply store to upgrade these items.

 

Project: Media Blast Cabinet Installation

Most blast cabinets can be set up and running in minutes. Be sure to cover all cars and other machinery in the area until you know exactly how much abrasive leaks out of your particular cabinet.

Use patience when blasting because it can be pretty slow going. Also bear in mind that your compressor needs a break. Even a small blast cabinet can keep your compressor running as long as you keep blasting, and your compressor needs some down time to cool off.

 

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As much as possible, use the blast cabinet to remove paint, rather than dirt, grease, and grime. This helps keep your abrasive material dry and usable longer.

Follow these steps:

Step 1:

Find a good spot in your shop to set up your cabinet. You want to select a place where you can look down into the cabinet at a good angle, with plenty of light, and have your arms comfortably fit into the holes provided for the gloves. Also, choose a space with plenty of access to the cabinet’s door. Finally, make sure that you have located the cabinet within range of your air compressor.

Step 2:

Bring the air hose to the cabinet. Most air hoses terminate in a female connection, so place the appropriate connector on your pressure regulator and a short length of hose on the output side of the regulator, with its own female end.

Step 3:

Most blasting guns use a barbed fitting or a male Industrial air fitting. Fit a length of hose securely to the blasting gun, and pass it out through the hole provided in the cabinet, making sure to get a good seal. The rubber grommet around the hole protects the hose from abrasion and ensures a good seal. Be sure the grommet is in place.

Step 4:

Connect the gun hose to the pressure regulator and set the dial to about 50 psi to the gun.

Step 5:

Pour about 2 to 3 pounds of abrasive into the bottom of the cabinet. You don’t need a lot because you change it frequently as it becomes dirty. The bottom of the cabinet is cone-shaped to effectively keep the beads recycling.

Step 6:

Connect the draw line to the gun; there is usually a metal pipe with a flexible length of hose. The pipe inserts into the reservoir of abrasive. The fl ex line connects to the front part of the gun.

Step 7:

The gun should have a ceramic tip. Theoretically, this tip is consumed in the course of work, but they actually last a long time. Unless you’re blasting every day, it’s reasonable to expect a tip to last years.

Step 8:

If you have access to an exhaust blower, install it and use the necessary plastic adapters to connect it to the vent located high on the cabinet back. Turn the exhaust vent on and direct the output to the outside of your shop before beginning the blasting process.

Step 9:

It is nearly impossible to get good results if you cannot see your work clearly. If you find that you need light, the best answer is a protected light source inside the cabinet. Stick-on LED lights with battery power work well for occasional use, or simply drill a hole in the side or back of the cabinet and wire in a small fluorescent lamp.

Step 10:

Adjust the pressure of the air until you achieve the best results. Guns and cabinets vary. In general, lower pressure ejects less material from the cabinet and is easier on the compressor.

 

Rust Removal

Rust is one of the more challenging obstacles to good powder coating, but with the right products it’s not that hard to remove. You can remove rust by mechanical means including brushing, sanding, and grinding, or by chemical means such as acid dipping or other chemical treatment. Any of these options can be a good choice. One is not significantly better than another, depending on the nature and location of the rust. If the rust is difficult to reach by mechanical means, you are limited to chemical rust removal. Most of the time, and depending on the extent of the rust, you may achieve the best results using both mechanical and chemical rust removal in turn.

 

To test the media blasting cabinet on rust, I chose this engine bay panel from an older Corvette restoration project. This panel has had a previous welding repair, and the whole thing was covered in rust.

To test the media blasting cabinet on rust, I chose this engine bay panel from an older Corvette restoration project. This panel has had a previous welding repair, and the whole thing was covered in rust.

 

This panel was a tougher project than the paint on the Mini wheel. Rust stands up better to the glass media than paint. But I kept at it until I got some results.

This panel was a tougher project than the paint on the Mini wheel. Rust stands up better to the glass media than paint. But I kept at it until I got some results.

 

With the rust removed, I could see the previous weld repair clearly. I will grind it smooth before I coat this part, and will also remove the plastic inserts.

With the rust removed, I could see the previous weld repair clearly. I will grind it smooth before I coat this part, and will also remove the plastic inserts.

 

I used the media blaster to remove most of the rust on this panel. I then switched to Eastwood Rust Dissolver to strip the panel, and used a wire wheel to finish it.

I used the media blaster to remove most of the rust on this panel. I then switched to Eastwood Rust Dissolver to strip the panel, and used a wire wheel to finish it.

 

As you remove the rust, look closely at the part. Has the rust gone far enough to weaken the structure, or even just enough to make it pitted and shabby looking? If the part has been weakened, consider using a welder or other means to reinforce the structure. Powder coat fills in some pitting, but if you wish to smooth the part before coating, Eastwood and other manufacturers make metal-based fillers that accept powder coat and survive the baking process.

Mechanical rust removal is just like any other mechanical cleaning method; it just takes longer because the rust has eaten into the metal instead of sitting on top of it as other grunge does. Be patient and use every tool you have to dig in and get the rust out.

Also, when you have something media blasted, work on it right away, because iron and steel rust very quickly once exposed to the atmosphere.

 

Written by Jeffery Zurschmeide and Posted with Permission of CarTechBooks

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