INSTRUCTION TO SERVICE
ITS: 6217
SECTION:

400- Underbody

WRITTEN BY:

Kalman Takacs

SUBJECT:

“NABI” – Chassis Corrosion Repair

ITS6217

THIS DOCUMENT AND THE CONTENTS DISCUSSED HEREIN ARE THE CONFIDENTIAL AND
PROPRIETARY INFORMATION OF NEW FLYER INDUSTRIES CANADA ULC AND NEW FLYER OF
AMERICA INC. AND ARE DISCLOSED BY NEW FLYER IN CONFIDENCE. THIS DOCUMENT AND THE
CONTENTS HEREIN ARE NOT TO BE DISCLOSED BY THE INTENDED RECIPIENT WITHOUT THE PRIOR
WRITTEN AUTHORIZATION OF NEW FLYER. ANY UNAUTHOIZED DISCLOSURE, REPRODUCTION OR
OTHER DISTRIBUTION OF THIS DOCUMENT OR INFORMATION IS STRICTLY PROHIBITED AND MAY
RESULT IN ACTION BEING TAKEN AGAINST THE PARTY MAKING THE UNAUTHORIZED DISCLOSURE.
THIS DOCUMENT AND ALL COPIES HEREOF MUST BE RETURNED TO NEW FLYER UPON REQUEST.

PROCEDURE:
1. Park bus on a flat surface and apply the parking brake.
2. Turn the main battery disconnect switch to the “OFF” position.
3. Position wheel lifts underneath the wheels.
4. Lift the bus to the appropriate height. Place jack stands underneath the official jacking pads.
NOTE: Only trained personnel can operate lifts. Follow safety instructions written on the lift and in the
NABI Maintenance Manual.
5. Before inspecting the underbody structure for corrosion, remove road debris and salt built up around the front
and rear axle area (see photo below). Use scraper, wire brush, pressure washer, etc. as required.

Figure 1: Road debris and salt built up on underbody structure
6. Inspect chassis from front to back and identify areas that needs to be repaired (see some examples below). If
corrosion was found follow the steps written below.

Figure 2 and 3: Example for corroded underbody surfaces

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Figure 4 and 5: Example for corroded underbody surfaces

Figure 6 and 7: Example for corroded underbody surfaces

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Surface Degreasing with Krown Enviro Solve:
For application and MSDS sheets of the Krown Enviro Solve, refer to Appendix A
7. If underbody surfaces are contaminated with grease and or oil (for example around air dryer, axles, hydraulic
reservoir, air tanks, etc.) then use Krown Enviro Solve degreaser and pressure washer to remove
contamination. Follow local regulations when disposing water contaminated with oil and grease.
8. Ensure that all drain holes at the bottom surface of the underbody tubes are clean so they are allowing for
drainage.
Krown Salt Eliminator Application:
For application and MSDS sheets of the Krown Salt Eliminator, refer to Appendix B
9. Spray the entire underbody with Salt Eliminator from Krown. This product can be sprayed with a foam cannon
or with a sprayer that is attached to a pressure washer. The Salt Eliminator will be foamed within 10-15
minutes. Wait 15 minutes then wash foam off with water. If dirt and debris still exist after first application,
repeat process on affected areas.

Figure 8 and 9: Spraying Salt Eliminator and foam built up on underbody structure
10. Let the underbody dry before continue the repair process. Compressed air can be used to blow off water and
dry surfaces.
11. Remove heavy corrosion from the affected surfaces. Use electric scaler and or grinder first then the 36G
abrasive wheel. Use different size and shape of wire wheels as required.
NOTE: Only the heavy scaling should be removed and do not need to remove all the rust because the
corrosion products need to be absorbed into the surface to properly treat the surface. If only rust staining
needs to be removed, use product Enviro Solve. Spray on and let sit for a couple minutes, scrub with a brush
and then rinse off with water.

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Figure 10 and 11: Spraying Krown Enviro Solve and scrub underbody structure with a brush
Bare Metal Surfaces:
For mixing and application of the PPG Zinc primer, refer to Appendix C
12. Degrease bare metal surfaces with Krown Enviro Solve.
13. Apply zinc primer by using an appropriate size of brush to the bare metal surfaces that have been cleaned off
with Krown Enviro Solve. Let primer dry per the instructions detailed in Appendix C.

Figure 12: Apply zinc primer to the underbody structure with a brush
14. Apply Sikaflex 221 sealer between stitch welds (A), around the joint edges of two steel components (B),
between wood floor and structure (C) as required. Refer to Figure 13.

C

A

B

Figure 13: Example for Sikaflex 221 sealer application

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Painting Large Open and Hard to Access Surfaces Showing Rust:
NOTE: For the application of the Rust Bullet product, refer to Appendix D.
15. For the large open and hard to access areas showing rust, apply the Rust Bullet product. This will need a
minimum of 2 coats. This product can be applied by brush, roller or spray gun.
Undercoat Application:
NOTE: For mixing and application of the PPG Undercoat (Corashield), refer to Appendix E.
16. Apply two light coats of Corashield undercoating to the primed surfaces, surfaces threated with Rust Bullet
and/or 372NF Cavity Wax. Also apply Corashield to the areas where the undercoating come off due to road
wear.
Krown T-40 Corrosion Inhibitor Application:
NOTE: For the application and MSDS sheets of the Krown T-40 Corrosion Inhibitor, refer to Appendix
F.
17. Apply Krown T-40 to the entire underbody by using the Krown spray system. Spray all fittings and electrical
connectors as well.
NOTE: The surface sprayed with Krown T-40 will look like “wet”. It will not cover up or hide anything that is
there. It will displace the moisture, protect the fittings and electrical connectors as well as supplement/support the
Corashield.

Figure 14: Application of T-40 to the entire underbody

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Cavity Protection - Coating the Inside Surfaces of the Underbody Steel Tubes
18. Ensure that the drain holes on the bottom of each underbody tubes are clean (no plugs!).
19. Spray Krown T-40 corrosion inhibitor inside the underbody frame tubes by using the Krown spray system.
Insert wand into the frame plug hole, push wand all the way to one end of the tube. Slowly pull back the wand
hose while spraying the T-40 corrosion inhibitor. Once back to frame plug hole push wand hose all the way in
the other direction. Slowly pull wand hose back while spraying. Repeat process on every frame plug hole
throughout the understructure of the bus including 24” up the vertical sidewall locations. Use borescope to
inspect cavities to ensure T-40 was applied correctly. The tubes do not need to be dry to apply the corrosion
inhibitor as it will displace the moisture. Once the product is applied, it will not dry up or cure. It is designed to
remain viscous so as to repel moisture. The foam will dissipate and it will penetrate any rust scale to create a
thin barrier on the metal to protect it.

Figure 15: Krown T-40 corrosion inhibitor application inside underbody steel tubes

Final Preparation / Reassembly:
20. Reinstall previously removed components.
21. Install new hardware as required.
22. Torque hardware per NABI Maintenance Manual.
23. Check for completeness of work.
24. Remove tools and unused parts from work area.
25. Remove jack stands and lower the bus.
26. Turn the main battery disconnect switch to the “ON” position.

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LABOUR ESTIMATE
Item

Operation

Men

Hours

1

Disconnect battery cables. Lift bus, inspect underbody.

1

1

Labor Time
M X HR
1

2

Pressure wash underbody, apply Salt Eliminator to underbody

1

2

2

3

Sand corroded surfaces, remove staining on underbody

1

3

3

4

Touch up sealant, zinc primer, apply Rust Bullet and undercoat

1

3

3

1

3

3

1

1

1

(Corashield)
5

Apply Krown T-40 to the entire underbody and inside the
underbody frame tubes

6

Reconnect / reassemble / refill as required, inspect, lower bus

Total hours: 13

PARTS REQUIRED
Item

Part Number

Description

1

6465149

Krown Salt Eliminator

2

6465150

Enviro Solve

3

115956

PPG Green Zinc Powdercoat S28080

4

108936

Urethane PPG Catalyst S28079

5

6465141

Krown T-40 Rust Inhibitor

6

235584

Undercoat PPG 7972W Corashield

7

NPN

8

055701

Rust Bullet
Sika 221 Sealer, WH

Qty.
per
Coach
5
1
0.2
0.4
3
1
1
0.5

Units

Notes

quart
quart
GA
GA
GA
quart
quart
EA

SPECIAL TOOLS REQUIRED
Item

Part Number

1

NA

Description

Qty.
per
Coach

Notes
Units

Pressure washer, borescope also See
Appendix B and F for required Krown tools

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Appendix A
Application and MSDS sheets of the Krown Enviro Solve

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Appendix B
Application and MSDS sheets of the Krown Salt Eliminator

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Appendix C
Zink Primer Mixing and Application Instruction
1.
2.
3.
4.

Clean area to be primed by using 36G abrasive disc and/or wire wheel.
Wipe dust off.
Degrease surface with industrial degreaser (Krown Enviro Solve).
Mix 1 part of PPG Catalyst S28079 (P/N 108936) with 2 parts of PPG Green Zinc Powdercoat S28080
(P/N 115956). No Varsol (thinner) is required. Mix thoroughly.
5. Apply mixture to the surface by brush.
6. Cure time is 4 hours at 77F (25ºC). Pot life of mixture is approximately 3 to 4 hours, BUT is significantly
reduced with exposure to air (moisture).

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Appendix D
Painting Large Open and Hard to Access Surfaces Showing Rust:

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Appendix E

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Appendix F
Application and MSDS sheets of the Krown T-40 Corrosion Inhibitor

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