Canada - Paint - Prevention And Repair Of Acid Rain Damage

Bulletin
0215

Issue Date
1991-06-01

Reference
BO-91-002

Model
All Models

Year Range
1986 ~ 2004

Market
Canada

Component
BO

Subject:
PREVENTION AND REPAIR OF ACID RAIN DAMAGE

"Acid Rain" is the result of rainwater or other airborne moisture made acidic by chemical impurities in the atmosphere. If these acidic compounds settle and remain in contact on an exposed vehicle, especially the horizontal areas of the hood, roof, and decklid, significant damage to the painted surfaces can occur.

It is the responsibility of the dealer to protect and maintain the quality of the vehicle's finish after receipt at the dealership. Frequent vehicle washing, up to 4 times weekly during high heat and humidity periods should be performed to minimize the potential for paint damage due to acid rain exposure. This is especially important in areas known for high frequency and concentration of acid rain and industrial fallout.

INSPECTION AND REPAIR:
Acid rain damage can frequently be identified on vehicles by the presence of visible spots on the paint surface which resemble hard water stains. Unlike water spots however, acid rain damage cannot be removed by polishing or buffing only.

Because of acid rain can etch and soften the paint, normal polishing or buffing repair procedures should not be attempted, as this will result in visible depressions in the paint surface.

CORRECTIVE ACTION:
The repair of acid rain damaged paint surfaces varies depending on how deep the acid has penetrated. Superficial damage can usually be removed by colour-sanding and polishing. If the damage extends to a depth greater than 1/2 mil of the clearcoat on a pearl or metallic colour, or more than I mil of a solid colour, machine sanding and repainting may be necessary.

Unfortunately, there is no simple method of determining the actual extent of the acid penetration other than colour sanding a representative affected area until there is no visible etching or depressions and then measuring the amount of paint removed with a magnetic type paint film thickness gauge.

REPAIR PROCEDURE FOR SUPERFICIAL TO MODERATE ACID RAIN DAMAGE: COLOUR SANDING AND POLISHING

MATERIALS AND SUPPLIES NECESSARY:

--> #1500 or #2000 grit wet-dry sandpaper
--> Rubber hand-sanding pad
-3M P/N 051144-05530, Meguiar's P/N E7200 or equivalent.

--> Liquid dishwashing detergent
--> Water pails
--> Baking soda
--> Rotary buffer, speed range 1200-2500 rpm (dual-action buffers may not adequately remove sanding scratches).
3M P/N 051144-05700 or Meguiar's "Hi-Tech" Finesse "Polishing Pad" or equivalent

--> Polishing Compound
3M "Finesse-It" P/N 051144-05923 or Meguiar's Mirror Glaze
#2 Hi-Tech Cleaner and #9 Hi-Tech Swirl Remover or equivalent.

CAUTION:
The following procedure should only be performed by personnel having prior experience with power rotary buffing to minimize the possibility of burning through or hazing the paint.

REPAIR STEPS:
1. Move vehicle out of direct sunlight and allow paint surfaces to cool if necessary. Dark painted colours become warmer in direct sunlight and require a longer period to cool off.
2. Add one (1) teaspoon of liquid detergent to a pail of clean water and allow wet-dry sandpaper to soak for several minutes in pail.
3. With vehicle surfaces cool, wash with soap and water and then neutralize with a baking soda and water solution (one (1) tablespoon of baking soda to one quart of water), followed with a thorough fresh water rinse.
4. Using a #1500 or #2000 wet-dry sandpaper with a rubber sanding pad, carefully sand the affected paint areas. Be sure to dip pad and paper in water frequently to prevent clogging of paper. During this process, also wipe down each sanded area frequently to determine if spots have been removed.

NOTE: When performing the above procedure, be sure to continuously measure paint film thickness during sanding with a Coating Film Thickness Gauge to prevent excess paint removal. A magnetic coating thickness gauge like the ELCOMETER 211 or equivalent is an ideal instrument to monitor paint film thickness during the colour sanding operation. Consult your local paint or tool jobber for pricing and availability. Remove no more than 1/'2-mil on clear coats, and no more than 1-mil an solids. Also be certain to always sand in one direction and never in a circular pattern.

5. After affected areas have been sanded, install one of the recommended buffing pads and set buffer to a speed in the range of 1200-1750 RPM for a Meguiar pad, 1500-2500 for a wool pad.

6. Apply recommended polishing material sparingly to about a 2-sq. ft. section of the affected panel and wipe buffer pad once across the area. Start buffer and polish area until haze of polish material is almost gone.

CAUTION!
AVOID APPLYING EXCESSIVE PRESSURE ON THE BUFFER TO PREVENT DAMAGE TO THE PAINT SURFACE.

7. Carefully inspect the polished paint area for remaining acid spots. If any are found, further sanding and polishing is necessary.
8. Proceed to polish and if necessary, re-sand the remaining affected areas. Be sure to continuously measure the paint film thickness during sanding to prevent excess film removal. Remove no more than 1/2 mil on clear coats, 1 mil on solids.
9. If the Meguiar's #2 Hi-Tech Cleaner is used, the #9 Hi-Tech Swirl Remover should also be used to produce a final finish. Always use a clean buffing pad when switching between polishing materials.
10. Apply and buff a non-silicone glaze to the polished areas if necessary to obtain a high gloss appearance.

REPAIR PROCEDURE FOR SEVERE-ACID RAIN DAMAGE : SANDING AND REPAINTING

If it has been determined that the acid damage has penetrated more than 1/2 mil on a metallic or pearl colour, or 1 mil on a solid colour, the following guidelines for sanding and repainting should be followed:

1. Using a rotary or dual action sander and #600 grit paper, completely sand the affected areas as required to eliminate any depressions or soft spots in the paint surface.
2. Wash vehicle with soap and water and then clean sanded areas with an appropriate silicone/wax remover (DuPont 3939, PPG DX330 or equivalent).
3. Apply a urethane enamel (DuPont Cronar, PPG Deltron, or equivalent) colour coat or colour/clear coat as required for maximum repair durability. Follow the paint manufacturer's recommendations for detailed application of paint and mid-coat adhesion promoter procedures as required.

NOTE:
Issue of this Technical Service Bulletin is to ensure that proper repair information is available. IT DOES NOT CONSTITUTE AN AUTHORIZATION FOR REPAIR. Normal provisions of the formal warranty policy, as applicable, will apply.