WORLDWIDE Design Guides
ENGINEERING GMW15359
Corrosion
STANDARDS
White Corrosion Rating Scale Guideline
perforate, or suffer significant metal loss, long
Introduction before 100% of its area becomes corroded.
Consequently, when rating a panel, one should
Note: Nothing in this standard supersedes
locate and rate the worst area on the panel. For
applicable laws and regulations.
components and fasteners, rating by estimating the
Note: In the event of conflict between the English percentage of visible corroded area is meaningful.
and domestic language, the English language shall If the proper rating actually falls between two rating
take precedence. values, the lower of the two rating values shall be
1.1 Scope. The purpose of the rating scale is to used.
allow comparison between vehicles and 3.1.1 Guideline Arrangement. The Guidelines are
consistency between personnel. It is important to arranged in four stand alone documents. The first
recognize that rating corrosion involves perception three guidelines consist of the cosmetic corrosion
of an objectionable surface and much of the rating scale and photographs pertaining to red rust.
judgment is subjective. The corrosion scales, The fourth guideline provides the same type of
provide some objective measure that will guide rating scale and photographs for white corrosion.
subjective judgment. The red rust guidelines consist of Sheet Metal
1.2 Mission/Theme. The Corrosion Rating Scale (GMW15356), Components (GMW15357), and
Guidelines contain corrosion rating scales, rating Fasteners (GMW15358). The White Corrosion
guidelines, and photographs for the determination Guideline (GMW15359) contains plated
of corrosion severity on all vehicular parts, components. Use of the white corrosion rating
including body and sheet metal, underbody and scale is not limited to this material, and can be
underhood components, and fasteners. It is used on any plating or material that exhibits white
intended that the scales are used for both corrosion. When rating a part, decide what type of
corporate corrosion inspections and field surveys. part is being rated and use the appropriate section
1.3 Applicability. This White Corrosion Guideline of the guideline. In all cases, use of a pictorial
contains plated components including EGR Valves, reference ensures consistent ratings and is easier
Headlamp Mounting Brackets and Additional to use than a strict written definition. The rating
Examples. guidelines may be helpful in determining the range
of photographs to use for comparison.
2 References Note: For further information, contact GM
Corrosion Engineering.
Note: Only the latest approved standards are
applicable unless otherwise specified. 3.2 Generic Rating Scale. The corrosion rating
scale reflects the various degrees of corrosion and
2.1 External Standards/Specifications.
ranks them as shown in the rating guidelines (see
None Appendix A, Table A1). On a scale of 1 to 10, 1
2.2 GM Standards/Specifications. represents perforation, 2 obvious metal loss, and
10 no visible corrosion (see Appendix A,
GMW3059 GMW15357 Table A2). Ratings from 9 to 3 reflect varying
GMW15356 GMW15358 degrees of corrosion from very little to extensive.
The photograph guidelines associated with this
3 Requirements scale will focus on showing examples of ratings 10
3.1 Using the Rating Scales. When rating parts through 3. These ratings are associated with levels
on a vehicle, one needs to consider the type of part of corrosion cosmetic in nature. Ratings of 2 and 1
being rated. To a customer, what is objectionable relate to significant metal loss or actual substrate
corrosion on a panel differs from that on a perforation, respectively, and are not included.
component or fastener as far as the total corroded 3.2.1 White Corrosion Rating Scale. While only
area is concerned. A panel is more likely to photographs of plated parts are shown, the rating
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scale may be used for any coating or material 7 Additional Paragraphs
which shows white corrosion. These parts should
7.1 Safety. All parts or systems supplied to this
be rated using the rating guidelines and by
standard must comply with the requirements of
comparing the appearance of the part to the
GMW3059, Restricted and Reportable
appropriate set of photographs.
Substances for Parts.
3.2.1.1 EGR Valve Rating Scale. Compare
component to the series of photographs in 8 Coding System
Appendix B and select the comparable level for the
rating. This standard shall be referenced in other
documents, drawings, etc., as follows:
3.2.1.2 Headlamp Mounting Bracket Rating
Scale. Compare component to the series of Rate per GMW15359
photographs in Appendix C and select the
comparable level for the rating. 9 Release and Revisions
3.2.1.3 Additional White Corrosion Examples 9.1 Release. This standard originated in May
Rating Scale. Compare component to the series 2006, replacing GM8103G. It was first approved by
of photographs in Appendix D and select the Global Laboratory Corrosion Testing
comparable level for the rating. Harmonization Team in June 2006. It was first
published in November 2006.
4 Validation 9.2 Revisions.
4.1 General. This rating scale along with the three Approval
additional rating scales defined in 3.1.1 “Guideline Rev Description (Organization)
Date
Arrangement” support the corrosion evaluation of
all GM laboratory and road corrosion related test A MAY 2009 Updated Section 3.1 to clarify
procedures in addition to material specifications. how rating scale is to be used.
(Material and Corrosion
5 Provisions for Shipping Engineering)
Not applicable. B JUN 2009 No change to content of
document. Republished to
6 Notes revise distribution requirements
from internal only to external.
6.1 Glossary. Not applicable. (Material and Corrosion
6.2 Acronyms, Abbreviations, and Symbols. Not Engineering)
applicable.
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Appendix A: Rating Scale and Guidelines
Table A1: Rating Guidelines
Panels Components Fasteners
10 NO VISIBLE CORROSION
ONE OR TWO SMALL WHITE
9 CORROSION SPOTS
SOME SMALL WHITE CORROSION
8 SPOTS
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MANY SMALL WHITE
7 CORROSION SPOTS
~ 10% WHITE CORROSION
MEDIUM SIZED WHITE 25% ± 15% WHITE
6 CORROSION SPOTS CORROSION
MANY MEDIUM SIZED 50% ± 10% WHITE
5 WHITE CORROSION SPOTS CORROSION
LARGE WHITE CORROSION 75% ± 15% WHITE
4 SPOT CORROSION
LARGE CORRODED AREA
3 OR VERY LARGE WHITE 100% WHITE CORROSION
CORROSION SPOT
2 METAL LOSS
1 PERFORATION
Table A2: Corrosion Rating Scale
Rating Description
10 No visible corrosion
9 Trace of corrosion
8 Slight corrosion
7 Light corrosion
6 Moderate corrosion
5 Medium corrosion
4 Mostly corroded
3 Totally corroded
Note 1
2 Severe corrosion
1 Perforation
Note 1: Corrosion resulting in obvious metal loss.
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Appendix B: EGR Valve Rating Scale Photographs
Figure B1: EGR Valve Rating 10
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Figure B2: EGR Valve Rating 9
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Figure B3: EGR Valve Rating 8
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Figure B4: EGR Valve Rating 7
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Figure B5: EGR Valve Rating 6
Figure B6: EGR Valve Rating 5
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Figure B7: EGR Valve Rating 4
Figure B8: EGR Valve Rating 3
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Appendix C: Headlamp Mounting Bracket Rating Scale Photographs
Figure C1: Headlamp Mounting Bracket Rating 10
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Figure C2: Headlamp Mounting Bracket Rating 9
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Figure C3: Headlamp Mounting Bracket Rating 8
Figure C4: Headlamp Mounting Bracket Rating 7
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Figure C5: Headlamp Mounting Bracket Rating 6
Figure C6: Headlamp Mounting Bracket Rating 5
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Figure C7: Headlamp Mounting Bracket Rating 4
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Figure C8: Headlamp Mounting Bracket Rating 3
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Appendix D: Additional White Corrosion Example Rating Scale Photographs
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Figure D1: Zinc Plated Rating 8
Figure D2: Cast Aluminum Rating 7
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Figure D3: Zinc Plated Rating 6
Figure D4: Zinc Plated Rating 5
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Figure D5: Bare Cast Aluminum Rating 5
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Figure D6: Zinc Plated Rating 4
Figure D7: Zinc Plated Rating 3
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