Engineering
Standards
Engineering Standard Number
Name COATING,ZINC PHOSPHATE
MATERIALS SPECIFICATION 74013
Identifier
(SURFACE,COATED)
1. Scope
This specification defines the requirements for fine grained cystalline zinc phosphate coating for
steel parts. This coating provides temporary or short time resistance to mild corrosion, controlled
lubricity and/or resistance to fatigue, wear, galling or scoring for components in moving contact
with other parts, with or without oil.
NOTE: Coatings supplied to this specification shall not contain hexavalent chromium.
2. Applicable Documents
Applicable documents listed below may be obtained from the respective organizations listed in
CES 10054, Standards Organizations Addresses.
a. ASTM B 767, Determining Mass Per Unit Area of Electrodeposited and Related Coatings
by Gravimentric and Other Chemical Analysis Procedures
b. CES 10054, Standards Organizations Addresses
c. CES 10056, Glossary
d. CES 60018, Weight, Coating
3. Definitions
There are no unique definitions in this standard. Terms used in this standard that have a general
definition for usage in Cummins Engineering Standards are defined in CES 10056, Glossary.
4. Specifications
4.1. Significance and Use
4.1.1. This specification defines the requirements for fine grained cystalline zinc phosphate
coating for steel parts. This coating provides temporary or short time resistance to mild corrosion,
controlled lubricity and/or resistance to fatigue, wear, galling or scoring for components in moving
contact with other parts, with or without oil.
4.1.2. This specification includes limits on pitting of the base material (Ref. Section 4.7
Pitting). It is recommended for use on critical fasteners and highly stressed components where the
presence of surface pits may adversely affect fatigue properties.
Current Release Number Std. Revision Level
142020-090 006 Page 1 of 4
CUMMINS CONFIDENTIAL
This document (and the information shown thereon) is CONFIDENTIAL AND PROPRIETARY and shall not be disclosed to others in hard copy
or electronic form, reproduced by any means, or used for any purpose without written consent of Cummins Inc.
Engineering
Standards
Engineering Standard Number
Name COATING,ZINC PHOSPHATE
MATERIALS SPECIFICATION 74013
Identifier
(SURFACE,COATED)
4.2. Process Requirements
4.2.1. The material to be coated undergoes the following general process: Components are
cleaned to remove grease and oil using an appropriate solvent and thoroughly dried. Parts are then
alkaline cleaned, rinsed in flowing water, immersed in phosphating solution for sufficient time to
obtain the required characteristics, rinsed in flowing water, immersed in sealant or rust preventative
as appropriate, and air dried.
4.2.2. The sealant shall not contain hexavalent chromium.
4.2.3. The supplier shall establish and document the parameters for process control which will
produce a coating meeting the requirements of this specification. This documented process shall
be used for manufacturing production material and shall constitute the “approved production
process.”
4.2.4. Once a coating process is approved for a component, that process shall continue to be
used unless a change is authorized in writing by representatives from Materials Engineering of
Cummins Inc., Cummins Technical Center. If it is necessary to make any change to the process
from what was originally approved, the supplier shall submit a request for written reapproval, with
a statement of the proposed changes in material and/or processing, and when requested sample
material and/or test data. The supplier shall obtain written authorization for process changes prior
to shipping parts to be used for manufacturing production material.
4.2.5. The documented process and control plan used for producing material in accordance
with this specification shall include but are not limited to the following process parameters:
a. degreasing and cleaning solution concentrations, temperatures and immersion times
b. phosphating solution concentrations for free acid, total acid, ferrous iron level, temperature
and immersion time
c. drying temperature and time
d. coupon weight measurements
e. visual inspection
f. verification of crystal size
g. approved source for chemicals used in processing
h. approved source for phosphate grain refinement additive
4.2.6. Coating weight for fasteners may be controlled using coupons of the same base material
type as the fasteners. Coupons shall be weighed and recorded for every batch. Thickness
measurement shall not be used for process control.
Current Release Number Std. Revision Level
142020-090 006 Page 2 of 4
CUMMINS CONFIDENTIAL
This document (and the information shown thereon) is CONFIDENTIAL AND PROPRIETARY and shall not be disclosed to others in hard copy
or electronic form, reproduced by any means, or used for any purpose without written consent of Cummins Inc.
Engineering
Standards
Engineering Standard Number
Name COATING,ZINC PHOSPHATE
MATERIALS SPECIFICATION 74013
Identifier
(SURFACE,COATED)
4.2.7. Documentation of the coating process and quality control records shall be made
available to Cummins Inc. representatives on request. There shall be a permanent record containing
results of all chemical analyses of the baths, adjustments to the bath, and periodic measurements
of operating parameters.
4.3. Appearance
Zinc phosphate coating shall be uniform and continuous in appearance and color (usually light gray
or dull black, finely crystalline, and nearly translucent), without stains, streaks and other evidence
of non-uniformity.
4.4. Coverage
The coating shall have a uniform, even, continuous distribution of phosphate crystals over all metal
surfaces significant to part operation, without bare spots. Visual inspection using a binocular
microscope may be used for in-process verification of coverage, uniformity and consistency of the
coating.
4.5. Crystal Size and Shape
4.5.1. The use of a grain refiner is mandatory to obtain a fine crystal structure.
4.5.2. The coating crystals shall be fine, blocky, prism-shaped crystals with rounded edges.
Flat, layered or spiraling structures are not acceptable.
4.6. Coating Mass
Coating mass per unit area shall be 0.6-1.0 milligrams per centimeters square. Mass per unit area
measurement shall be made according to ASTM B 767. Use of stripping solution as described in
CES 60018 is recommended.
4.7. Pitting
Pitting of the base material shall not exceed 10 micrometers.
Current Release Number Std. Revision Level
142020-090 006 Page 3 of 4
CUMMINS CONFIDENTIAL
This document (and the information shown thereon) is CONFIDENTIAL AND PROPRIETARY and shall not be disclosed to others in hard copy
or electronic form, reproduced by any means, or used for any purpose without written consent of Cummins Inc.
Engineering
Standards
Engineering Standard Number
Name COATING,ZINC PHOSPHATE
MATERIALS SPECIFICATION 74013
Identifier
(SURFACE,COATED)
Appendix A: Figures
Fine grained zinc phosphate coating shown at 500X in a scanning electron micro-
scope. Note, the uniform coverage of the surface with no bare metal.
Figure A1: Typical Appearance of Zinc Phosphate Coating
Current Release Number Std. Revision Level
142020-090 006 Page 4 of 4
CUMMINS CONFIDENTIAL
This document (and the information shown thereon) is CONFIDENTIAL AND PROPRIETARY and shall not be disclosed to others in hard copy
or electronic form, reproduced by any means, or used for any purpose without written consent of Cummins Inc.
