Chapter 7 Body Shop Materials

Objectives Select the right repair materials for the job Explain the basic purpose of common body shop materials Compare the use of similar shop materials Summarize when to use different kinds of body filler and putty Know how to select the right type of primer and paint

Introduction Collision repair materials include various fillers, primers, sealers, adhesives, sandpapers, etc. When consumers look at a vehicle’s paint job they often see a shiny bright color Hidden technology under the surface of the paint Professional collision repair and refinishing technician understands the chemistry and skill needed to do high-quality repairs

Refinishing Materials Car body is protected and beautified by a complete finishing system Refinishing materials is a general term for the products used to repaint the vehicle New paints last longer but require skill and safety measures The substrate is the steel, aluminum, plastic and composite materials used in vehicle construction Paint beautifies the body and protects the metal from rust

Primecoats and Paintcoats Basic paint job on a car consists of several coats of two or more different materials Primer has to improve adhesion of the paint and is the first coat applied Paint will not adhere to the substrate without a primer coat Colorcoat is the paint applied over primecoats –Several light coats Basecoat-clearcoat paint systems use clearcoat over colorcoat

Paint Types General types of paint include enamel/urethane and waterbase/waterborne Enamel finishes are catalyzed – use a hardener Once applied these materials dry in two-stages –Some solvents used to thin or reduce material must evaporate –Chemical reaction occurs within the material and causes it to harden or “cure”

Paint Types (continued) Catalyzed enamels cure with a gloss that does not require polishing Two-stage paints consist of two distinct layers of paint: basecoat and clearcoat Basecoat-clearcoat enamel is the most common system used to repaint cars and trucks –Layer of color is applied over the primecoat of primer or sealer –Coat of clear is sprayed over the color basecoat

Paint Types (continued) Acrylic urethanes are slightly harder than plain acrylics Waterbase/waterborne paints use water to carry the pigment –Help satisfy stricter emissions regulations –Serve as an excellent barrier coat

Original Equipment Manufacturer (OEM) Finishes OEM finishes (factory paint jobs) are thermo- setting high-solids basecoat-clearcoat enamels or waterbased low-emission paints Common finishes are baked in huge ovens before installing interior and nonmetal parts Vehicle manufacturers use several types of finish materials, coating, application processes Most common OEM coating processes include two-stage, three-stage paint, multistage, single- stage, powder coat

Contents of Paint Paint’s chemical content includes pigments, binders, solvents and additives Pigments are fine powders that impart color, opacity, durability to the primer or paint Large reflective pigment flakes are added to metallic color High-solids materials are needed to reduce air pollution or emissions while painting Binder holds the pigment particles together, and helps the color stick to the surface

Solvents Solvent/reducer is the liquid solution that carries the pigment and binder Reducers are composed of one or several chemicals and provide a transfer medium Solvents are volatile and used to thin a paint for spraying and evaporate as the paint dries Thinning and reducing determine the viscosity to spray out smoothly onto the surface

Solvents (continued) Some water-based paints come premixed and are not reduced Distilled water can be added to water-based paints to make a thinner solution Water used for equipment cleaning contains hazardous materials and is hazardous waste –Do not pour down the drain –Do not combine with other waste solvents

Additives Speed up or slow down drying Lower the freezing point of a paint Prevent the paint from foaming when shaken Control settling of metallic and pigments Make the paint more flexible when dry

Drying and Curing Drying changes a coat of paint or other material from a liquid to a solid state Flash time is the first stage of drying when some of the solvents evaporate Retarder is a slow-evaporating solvent or reducer that is used to slow the drying process Accelerator is a fast-evaporating solvent or reducer for speeding up drying time –Needed in very cold weather Catalyst causes a chemical reaction

Primers and Sealers Plain primer is a thin undercoat designed to provide adhesion for the paint –Used when the surface is smooth Self-etching primer has acid in it to prepare bare metal so the primer will adhere Epoxy primer is a two-part primer that cures fast and hard –Greatly increases body filler adhesion and corrosion resistance over bare metal

Figure 7-4. Primers are needed for the paint to bond to the substrate securely. There are many variations such as primer-sealer that increases adhesion and also blocks out any color or chemical differences of the old paint

Sealers Bleeding or bleedthrough means colors in old primecoat or paint seep into new paint Sealer is a midcoat between the paint and the primer or old paint to prevent bleeding Sealers cannot be used as a primer Primer-sealer provides the same protection as primers but also seals over a sanded old finish to provide uniform color holdout

Primer-Surfacers Primer-surfacer is a high-solids primer that fills small imperfections and usually must be sanded –Often used after filler to help smooth the surface Primer-surfacers are used to build up and level featheredged areas or rough surfaces Good primer-surfacer should be ready to sand in as little as 30 minutes Primer-filler is a very thick primer-surfacer

Use a Complete System! Always use a complete refinishing system Refinishing system means all materials are compatible and manufactured by the same company Mixing materials from different manufacturers can cause problems –Chemical contents of different systems may not work well together

Figure 7-7. The mixing room contains all of the ingredients used by the shop’s painter or refinish technician. The small room has extra ventilation to remove paint fumes while mixing paint or primer ingredients. Only mix and use paint materials from the same manufacturer or paint system.

Other Paint Materials Wax and grease remover is a fast-drying solvent often used to clean a vehicle Flattener is an agent added to paint to lower gloss or shine Flex agent, or elastomer, is an additive that allows primers and colors to flex or bend Rubberized undercoat is a synthetic rubber material applied as a rust preventive layer Corrosion is a chemical reaction of air, moisture, or corrosive materials on a metal surface

Body Fillers Filler is a material used to fill a damaged area Mixing board is the surface used to mix filler Light body filler is used as a very thin top coat of filler for final leveling Fiberglass body filler is used where rust repair or strength are important Using too much hardener is a common mistake –Causes the filler to set before you have time to spread it, among other problems

Figure 7-8. A body filler is a two-part material that is mixed together and then applied over small dents in metal body parts. The body filler will heat up and cure in a few minutes so it can be sanded.

Glazing Putty/Finishing Fillers Glazing putty is for filling small holes or sand scratches Spot putty has more solids than glazing putty –Should not be used for large surface depressions Two-part putty comes with its own hardener Some two-part putties can be applied over paint to reduce sanding time

Masking Materials Overspray is unwanted paint spray mist floating around the spray gun Masking paper is designed to cover body parts not to be painted Masking plastic should not be used next to area being sprayed –Paint can drip onto the body surface Wheel masks are preshaped to fit over wheels

Masking Materials (continued) Fine-line masking tape is very thin and smooth –Produces a better paint part edge Duct tape protects parts when grinding or sanding Masking liquid or coating is usually a sprayable material for protection from overspray Masking liquid washes off with soap and water

Abrasives An abrasive is any material used for cleaning, sanding, smoothing, or material removal Grit refers to a measure of the size of particles on sandpaper or discs Grit numbering system denotes how coarse or fine an abrasive is Very coarse grit (16 to 60) quickly removes paint and takes it down to bare metal Generally start with the finest grit that is practical

Grinding Discs Grinding discs are round very coarse abrasives used for initial removal of paint, plastic, metal Some are thick and do not need a backing plate Disc backing plate is mounted on grinder spindle Grinding disc size is measured across outside diameter Most common sizes are 7 and 9 inches –175 and 225 mm

Figure Various abrasives or grinding-sanding materials are used to remove the old paint and to sand the body filler and paint before refinishing. Here the body technician is using a very coarse grinding wheel to remove paint before application of the body filler.

Sandpapers Sandpaper is a heavy paper coated with an abrasive grit Sanding sheets are square and can be cut to fit sanding blocks Dry sandpaper is designed for use without water Wet sandpaper uses water to flush away sanding debris Wet sandpaper blocks sand paint before compounding or buffing

Scuff Pads Scuff pads are tough synthetic pads used to clean and lightly scratch surface paints and parts Handy for scuffing irregular surfaces –Door jambs, inside of the hood and deck lids, etc. Scuffing cleans and lightly scuffs these areas so the paint, primer or sealer will stick

Compounds Compounding involves using and abrasive paste material to smooth and bring out the paint gloss A hand compound is applied by hand Machine compound is applied with an electric air polisher and will not cut as fast Rubbing compound is the coarsest type of hand compound and will remove paint or clear Hand glazes are for final smoothing and shining of the paint, and are applied by hand like a wax

Adhesives Adhesives bond parts to one another Weatherstrip adhesive holds rubber seals and similar parts in place Plastic adhesives or emblem adhesive is used to install emblems and trim onto painted surfaces Adhesive release agent is a chemical that dissolves most types of adhesives

Figure Here the detail technician is using a high-speed buffer to polish the paint surface. On new paint, it will increase smoothness and gloss. On old paint, it will remove the oxidized or dulled paint surface and uncover the bright, original color again.

Epoxies Epoxy is a two-part glue used to hold various parts together Two ingredients are mixed in equal parts Mixture cures through a chemical reaction Always use the type of epoxy suggested by the vehicle manufacturer

Sealers Sealers prevent water and air leaks between parts Seam sealers make a leakproof joint between body panels Tube sealers are applied from a tube or with a caulking gun Silicone sealers are not paintable and should not be used in auto body repair Ribbon sealers must be worked onto the parts with your fingers

Hazardous Materials Hazardous material is any substance that can harm people or the environment Material safety data sheets (MSDS) detail chemical composition and safety information Employers must know the general uses, protective equipment, accident or spill procedures for safe handling Right-to-know laws give information and stipulations for working with hazardous materials General intent of the law is for employers to provide employees with a safe working place

Hazardous Materials (continued) Irritants can affect your lungs, skin and eyes and could affect your health Toxins are poisonous substances –Neurotoxins affect your nervous system –Liver toxins damage your liver –Reproductive toxins can cause birth defects –Blood toxins damage your red blood cells Corrosives burn your eyes and skin Carcinogens cause cancer Allergens cause allergic reactions

Waste Disposal and Recycling Many shops use full-service haulers to test and remove hazardous waste from the property Hauler takes care of paperwork and deals with government agencies Some shops recycle materials so that it can be reused to clean spraying equipment Solvent recycling machine removes impurities from solvent Impurities are filtered out and stored in a plastic bag for proper disposal

Summary Collision repair materials include fillers, primers, sealers, adhesives, sandpapers, etc. Substrate is the metal, aluminum, plastic or composite used in the vehicle construction Two types of paint: enamel and water-base Filler is used to level a damaged area Masking materials protect body parts from overspray Sealers prevent water and air leaks between parts