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The owner of this Mazda RX7 was concerned that the structural integrity of the vehicle’s A-pillars was compromised by the visible corrosion damage around the upper hinges. The difficulty in evaluating this type of issue is that the problem is not completely exposed until the area is opened up to expose the internal structure.
Upon the initial inspection and appraisal, it was identified that the upper hinge fixture point on each side were indeed corrosion fatigued. The doors were dropping when opened and the owner had to lift the rear section of the door to close them. This was placing excess strain on the door handles and it was damaging the paint on the sill and quarter panels.
The initial objective was to remove the doors and fenders to gain access to the problem and ascertain the extent of the damage.
The RHF skirt reinforcing beneath the fender was removed to expose the complete pillar section and allow ease of access and repair of the damaged area.
Next the external A-pillar (top hinge) cover panel was removed to expose the full extent of the corrosion damage to the internal hinge (fixture point) reinforcement structure.
Now given these circumstances it’s prudent to further investigate other factors that may have contributed to the issue (ie window, plenum chamber, drip rail or turret perforation) and rectify these causes to eliminate the risk of re-occurrence.
After eliminating the probable causes, the actual issue was identified to be condensation ingress between the external panel skin and the pillar hinge reinforcement.
The extent of the corrosion pitting was concentrated to the external surface of the internal hinge fixture reinforcement panel. Although mostly superficial, the upper section had perforated substantially and the fatigued is clearly visible after the sandblasting process.
Now that the internal hinge reinforcement structure is exposed, the next step in the process was to sandblast the corrosion effected area, identify the extent of the corrosion damage and rectify the structural integrity.
After the sandblasting process, the areas are etch primed to seal the exposed metal from the elements and then the subsequent repair work can commence.
The internal hinge reinforcement structure damage was sized and a duplicate steel plate was fabricated to suit the area.
The weakened corroded section was cut out (completely removed) and the duplicate steel plates were fuse welded into position.
The corrosion repair area was sandblasted again and etch primed for atmospheric protection.
Next the external A-pillar top hinge panel needed to be duplicated and welded in place. An exact replica was fabricated by René Farrace, then it was fitted and fuse welded into the correct position.
Again the corrosion repair area was sandblasted and etch primed.
The front skirt reinforcement panel was then fitted and welded to complete the structural repair.
Please remember that the sequence of repairs will be determined by the extent of the damage. Don’t take shortcuts with structural areas, because in an accident it could be the difference between life and death.
My advice to the DIY’s, is careful planning and attention to detail are the basics required to successfully execute the rectification schedule. Set out with one objective in mind, to do right the first time!
If time is of the essence, research the availability of a professional with the desired skills to carry out all or part of the repairs. Alternatively, if you’re budget poor but good with your hands, DIY it! I’ve met numerous industry practitioners with either no idea or no inclination to step outside the square. But in times of economic depression they will gladly take your money.
Sandblasting is a must do! Do not compromise this step by wire brushing as this will only polish the surface or grinding as this will miss the crevices and pits of corrosion. Sealing exposed metal is equally as important especially as the repair will take time and atmospheric conditions change seasonally. The pitfall of using a media like Garnet is that it will break down into fine particles and find its way into the isolation of extruded sections. You owe it to yourself to make every effort to remove all or as much of this media as possible or risk creating another issue.
When sealing the repairs use compatible materials from the base to top coat finish. Too many times I have seen it before where incompatible products have been used and are mixed together. Although the underlying problem is not instantly visible, over time it will give you grief.
By René Farrace