Bodywork Preparation Prior to Repainting
Figure 1
The only way of being sure that the body panels are in good condition is to completely strip off the old paint. Good quality paint stripper will effectively remove cellulose paint, with minimum damage to the panels, but it is unable to remove rust and filler. However, it makes life a lot easier if used prior to wire brushing. Wire brushing with an electric drill was the method I used, but if I had found a suitable area away from the garage, I would have tried shot blasting. Shot blasting is quick and effective. The drawbacks are the ammount of dust produced, extra expense of equipment and the care required to protect the surface of the metal from damage.
When I examined the inner wings, , the rear ends were corroded, and in need of repair, but the remaining area of the panels appeared to be in reasonable condition. However, the paint was hiding an insidious condition known as " filiform corrosion". which manifests itself as fine thread like filaments of rust on the surface of the metal (see Figure 1). This is caused by galvanic action and is not confined to steel. Aluminium alloys used in car bodywork can also suffer from this condition, particularly when the protecting paint layer is inadequate. Unfortunately filiform corrosion often goes unnoticed until the paint film fails and blisters. Apparently cellulose paint does not offer good protection against it, so adequate anti corrosion treatment must be applied to the panels before applying cellulose paint. Proprietary products containing phosphoric acid are often supplied as kits containing rust remover and corrosion preventer.
If the car has painted wire wheels, the only practical method of preparation before painting is shot blasting. It removes all traces of rust and provides a really good texture for painting. Professional shot blasting services can be found at a reasonable cost in most areas.
Perfecting body contours
Where corroded metal has been removed, new parts must be welded in and the external seams ground flush. Body contours on and around the ground welds may not be perfect. Raised parts of a panel will have to be slightly depressed and filled. 2 part polyester fillers are easy to apply and sand down. The area to be filled should be degreased and abraded with grade P80 wet and dry paper. The filler is thoroughly mixed with a small quantity of hardener and has to be applied within 4-5 minutes. Sanding down can usually begin within 30 minutes. The edges of the filler must be perfectly feathered.
An alternative to using polyester filler is lead loading. This involves using a high lead content solder to fill imperfections in steel panels. The advantage of using this technique, is that it will not crack if the panel flexes. To apply it to a steel panel, a special solder paste containing flux must be brushed on to the surface before melting lead solder on it. See details of the technique on the bottom of the Mig Welding page under the Bodywork option on the menu. I used lead loading when I repaired the rear wings. The reason I used it there is because I felt a certain amount of flexing may be experienced where the rear wings are bolted to the front ones. So far the paint has not cracked at the welded joint.
Morgan front wings manufactured before 2004 were not rolled from a single sheet of steel. They were made out of 3 separate pieces welded together as shown in Figure 2. The wings were not made by the Morgan Motor Company, because they did not have rollers large enough. When the wings were prepared before painting, a polyester type filler was used over the welds to perfect the body contours. Sometimes the paintwork cracks along the welds on old Morgan front wings and the filler covering the welds of the headlamp nacelles may also crack. If the cracked filler and paint film is not repaired, water seeps in and rust forms.
Morgans manufactured after 2004 are constructed with Superform aluminium front wings. A single sheet of aluminium is heated to 500 degrees centigrade and moulded into shape. These should maintain their finish for a long time. However, rebuilding a Morgan with the older type of wings will require stripping them back to bare metal and applying filler or leaded solder over the welds. I used a polyester type of filler around the headlamp nacelles, because it was a lot easier to shape, but in retrospect, I feel it would have been better to use body solder.
It is worth restoring the original front wings, because the new superform type are expensive. At the time of writing, I believe two new front wings would cost in the region of two thousand pounds. They may also differ in shape slightly from the originals. If this is so, the original bonnet panels may not fit properly.
Figure 2
The Painting Stages
Stage1 Thoroughly clean, de-rust and renovate the chassis, front inner wings and bulkhead. Prime and paint them with an anti rust paint.Check with the manufacturers instructions on mixing the paint and which thinners should be used to clean the spray gun. Try to produce a really good finish on these parts, because not only will they be visible in the engine bay, but any deterioration under the paint film will be more obvious. Figure 4 shows the condition of my engine bay before and after the restoration. Hammerite manufacture anti rust paints in aerosol cans, which produce an excellent finish and can save time preparing and cleaning the spray gun. There is no need to buy extra paint of the same batch for colour matching either, because most of these items are hidden from view. The best treatments for the chassis, are galvanising or powder coating, but these processes will be expensive. If you are fortunate enough to own a new Morgan, the chassis will have been treated with either of these processes. The latest V8, Plus 6 and Aero Morgans, have an advanced aluminium chassis of course.
Leave the freshly painted panels a few days to allow the paint to harden, then assemble the bulkhead and front inner wings on the chassis. Where the front inner wings butt up against the bulkhead, use a good sealant between the panels, to exclude future ingress of water. DO NOT USE SILICON SEALANT, It will reject paint used for any later touching up. A sealant between the flange on the bottom of the inner wings and the chassis, will also prevent water from entering the joint and corroding the steel.
Figure 4
Stage2 Rebuild, paint and fit the engine, gearbox, propshaft, shock absorbers, suspension, hand brake and fuel tank. Painting and fitting these components at this stage is so much easier than doing so with the body and wings in place. These components should also be mechanically restored to the highest standard before refitting, particularly when a vehicle over 40 years old, no longer requires an MOT. Carefully priming and painting them to a high standard, will not only make servicing a more pleasant experience, but it will increase the value of the vehicle. Hammerite produce a black gloss paint which can be applied to rusty steel panels. During a rebuild, no panel containing rust should be re-installed. However this paint can be used on clean rust free panels, as it acts as a rust protector, primer, undercoat and topcoat. It comes in 5 ltr containers or 600ml aerosol cans. They also produce a stone chip resistant paint for use in high abrasion areas, such as wheel arch undersides. Hammerite also supply underseal. When I removed the body of my Morgan and was confronted with the scene shown in the left hand photograph of Figure4. I never dreamed that I could restore it to the condition shown in the right hand photo. However, using the correct products and adhering to the manufacturers instructions made the job straightforward.
Figure4
Stage3 Trial fit the ash frame and check everything lines up perfectly. Make any adjustments before treating the frame with Cuprinol. Prime and paint it with good quality external paint. This can be applied with a brush. When the paint has been given sufficient time to dry, coat the underside of the sill boards with underseal. The frame is mounted on a damp proof course, which is sandwiched between sill boards and the chassis. The original damp proof course on my Morgan appeared to be a thick tar like tape. The stuff I used as damp proof course was a thick grease impregnated felt anti corrosion tape. I can't remember who manufactured it, but it looks like Denso tape. As the sill bolts were tightened, some of the greasy content oozed out. I can't imagine any water getting between the sill boards and chassis now.
Figure 6
Stage4 The scuttle, quarter panels, rear wheel arches, doors, inner and outer rear panels should be trial fitted. Particular attention should be paid to the door. If it has been renovated check that the door can be opened and closed without fouling the weatherproof wire beading. The curvature of the door is greater at the top and has a larger angle from vertical at the front than the rear. This is known as slam.If the door does not follow the lines perfectly, the slam is not correct and it will be prone to rattle, even when the striker plate is adjusted. Also check the gap around the door frame. Any modifications must be made at this stage, because bending a panel after painting will damage the finish..
Figure 7
Stage5 After ensuring the panels mentioned in stage 4 fit together perfectly, carefully remove, degrease and thoroughly clean them. Check for any pitted steel and treat it with a proprietary anti rust product containing phosphoric acid. The body of mass produced cars go through a series of cleaning procedures before they are submersed in a phosphating solution, where they are electrophoretically painted. This forms an anti corrosion layer called an "E-coat". Before the cars go into the paint shop at the Morgan factory, they are cleaned with an acid wash protection. There are companies advertising E-coating services on the internet. However this process is very expensive. For the DIY rebuild, phosphoric acid based products are the only economic option.
Stage6 Prime and paint the inside of the panels with an anti rust paint. Before applying any paint to a rust free and clean panel, wipe it down with acetone. This will remove any grease from your hands that have contaminated the panel due to handling. Finally wipe down the surface to be painted, with a tack cloth. Paint the inside of the panels with anti-rust primer, then apply several anti-rust top coats. The rear inner panel should be painted on both sides at this stage.
Figure 8
Stage7 Fit the scuttle, quarter, rear, and wheel arch side panels to the ash frame, before painting their outer surfaces. Most production vehicles are constructed with monocoque bodies. Respraying these vehicles usually involves applying each layer of paint over the whole body in a single operation. The modular nature of the Morgan body enables many panels to be sprayed before assembling them on the car. This increases the chances of a beginner to obtain a top quality finish. Correcting a fault on an individual panel, means not only less work, but provides experience before moving on to the next. However the panels listed at this stage, require pinning and screwing to the ash frame, which would cause damage to the finish if they were painted before fixing them.
Stage8 Prepare, prime and topcoat the body panels. The thoroughness and time spent in preparation will pay dividends when painting a car body. Preparation takes far longer than painting the car. This is why paint shops charge so much to respray a car. There are four main processes required to produce a satisfactory finish, as indicated in Figure 8 (A-D)
A After thoroughly preparing the bare metal panels, they must be cleaned with acetone and wiped over with a tack cloth, then sprayed with an etch primer-filler. The data sheet must be consulted before using this product. Flash off times must be adhered to before re-coating, otherwise trapped solvent may cause paint film failure. Separate etch paint and primer-filler paints can also be used. After applying several coats of the high build primer filler, a guide coat of dark colour paint is dusted lightly over the panel. This can be applied with a cheap aerosol can of paint. The panel is then rubbed down using a long block with 80 grit, followed by 150 grit aluminium oxide paper. Do not use sand-paper, because the sand grains are only bonded weakly to the backing paper. It is important NOT to use the rubbing down paper with your fingers, as this will cause an uneven surface that looks much worse when the top coat is applied. Keep rubbing until most of the guide paint is removed. Stop rubbing when only small patches of guide paint remain.The sanding process should be carried out in two directions at right angles with each other.
Figure 8
B Dark patches will indicate low spots. If they are deeper than the layer of etch primer-filler, they can be filled with cellulose putty, which is ultra fine filler paste for minor depressions. It is not suitable for filling deep indentations. Small bright metal patches indicate high spots and will have to be dressed flat with a polished panel beating hammer. The panel must be thoroughly cleaned with a damp cloth. When it is dry, wipe it with a tack cloth to remove any traces of dust, before applying two or three more coats of the filler primer. When the primer coats are fully dry, repeat the guide coat process described in section (A) until all the guide coat can be removed and no bright metal shows through the primer. Finish the the block-sanding with 300 grit wet and dry paper used wet. If carried out carefully, block-sanding should ensure imperfections are eliminated are eliminated.
C Thoroughly clean the panel and apply several more coats of primer, taking care to allow flashing off time between them. Block sand the final coat with 400 grit wet and dry paper used wet. The most effective way to check check the panel for imperfections is to lightly run your finger tips over it. It is more difficult to spot imperfections in the primer coat with your eyes, than with your hands. Handling the primed finish before top coat is applied can leave unwanted grease on the surface. Acetone cannot be used to clean the cellulose finish, because it would dissolve the paint. Panel wipe may be OK, but check with the supplier whether it will react with cellulose paint.
D Reading the manufacturers data sheet is essential when applying any paint, but it is critical if the gloss coat is going to be of the highest quality and remain so for many years. The viscosity of the paint and ambient temperature are important. Paint from the can is too thick to spray. Pure cellulose virgin, anti-bloom thinners should used to mix with the paint. At 20°C most cellulose is mixed 1:1 with thinners when applying the initial layers of top coat. I used 4 to 5 thin layers of top coat rather than 3 heavy coats. I allowed at least 30 minutes at 20°C between coats to allow the paint to flash off. This avoided runs. I left the top coat for at least a week before rubbing the paint down with 1600, wet and dry paper used wet on a block. The paper was washed and changed regularly to prevent it from clogging. Finally I applied a couple of coats of paint mixed with 70% thinners. This was left another week and finished off with 2000 grit paper, followed by t-cut. The car shone like a diamond. The paint is still in good condition to this day. Leaving the paint for a week before rubbing down may seem excessive, but there were other panels to paint and preparing them, occupied most of my spare time.
The Car Thirty Years After the Rebuild
Figure 9
