Material

Specification

Finish (Coating)

GMW3359

Non-Electrolytically Applied Zinc Rich Coating

1 Scope

This specification covers the basic requirements for

a corrosion resistant non-electrolytically applied zinc

rich coating. Besides corrosion protection the coat-

ing also provides color identification and lubrication

by using an additional topcoat with integrated lubri-

cant such as wax or PTFE.

1.1 Material Description. The material to this spec-

ification covers organic or inorganic zinc flake coating

with and without organic topcoat. This coating system

must be free of hexavalent chromium, with no hexava-

lent chromium in final product per GMW3059 require-

ments. GMW3034 will be used as a referee test. This

coating process does not generate hydrogen, how-

ever, pretreatment processes i.e. acid pickling could

cause hydrogen adsorption. Non-electrolytically ap-

plied zinc rich coating has high permeability, which al-

lows effusion of hydrogen during curing which might

have been absorbed during acid pickling.

1.2 Cross-Reference of Replaced Specifications.

GMW GMW3359

Delta Motors

GM do Brasil

GM Holden

GM NAO GM7114M

ISUZU

ITDC GME00255

SAAB

1.2.1 Specifications Qualified to this Material

Specification. Not applicable.

1.3 Symbol. Not applicable.

1.4 Typical Application. This coating is suitable for

externally and internally threaded parts (size greater

than or equal to M6) and non-threaded ferrous parts

where high level of corrosion protection and freedom

from hydrogen embrittlement are required. This is not

recommended for the following:

• Bolts and nuts of sizes < M6

• Parts with internal drive recess

• Against magnesium surfaces

• Washers of all sizes

• Parts where electrical conductivity is required

1.5 Remarks. Use of this coating system on

threaded surface and/or bearing surface of joints

could effect the torque-tension relationship. It is

recommended that a torque-tension study of the

fastener joint be performed before releasing this

finish on any new application.

2 References

Note: Only the latest approved standards are appli-

cable unless otherwise specified.

2.1 Normative.

DIN946 ISO 11014-1

ISO 1463 ISO 9227

SAE/USCAR-5 SAE/USCAR-11

2.2 GM.

GM7114M GM9071P

GM9501P GM9509P

GM9540P GME00255

GMW3034 GMW3059

9981228 9984094

9985670

3 Requirements

3.1 Requirements on Delivery.

3.1.1 Chemical Requirements. Not applicable.

3.1.2 Mechanical Requirements. Not applicable.

3.1.3 Physical Requirements.

3.1.3.1 Appearance. The coating shall have a uni-

form appearance and shall be free from tears, sags,

pores, cracks, flakes, blisters, rough spots, uncoated

areas and excess coating which affects appearance

and performance. The coating shall not be oily or

tacky to the touch. During normal handling practice

parts shall not leaveparticulate residue on equipment,

Originating Department: North American Engineering Standards, Records and Documentation

December 2000 Page 1 of 4

GMW3359 GM WORLDWIDE ENGINEERING STANDARDS

hands, or gloves. The coating shall be completely

cured and shall have good adhesion to base metal.

The color unless otherwise specified shall be silver.

3.1.3.2 Thickness. When applied to threaded prod-

ucts, the coating shall not have an adverse effect

on normal installation and removal practices. At the

same time coating thickness shall be adequate to pro-

vide corrosion resistance performance requirements.

3.1.3.2.1 The maximum thickness of coating which

may be applied to threads on threaded products is

limited by the basic thread size (tolerance h or H).

After coating, parts must gage with appropriate ba-

sic size GO thread gages. Threads may be produced

undersize/oversize (before coating) to accommodate

the coating thickness, provided the finished product

(after coating) meets all specified mechanical prop-

erties. Where mechanical properties are not speci-

fied, undersizing/oversizing is subject to approval by

the pertinent engineer and all undersize/oversize shall

be within permissible limits as agreed upon.

3.1.3.2.2 The maximum coating thickness under the

head of bolts and screws shall not exceed 25 µm.

Supplier shall monitor the thickness and maintain

the test results in file to be submitted when required.

ISO 1463, microscopic test to measure the thickness

of coating shall be used as a referee test.

Note: If the part is phosphated, it is recommended

that the phosphate coating be fine crystalline of 3 µm

maximum. coating thickness.

3.1.4 Additional Requirements.

3.1.4.1 Corrosion Resistance. Parts coated to

this specification when neutral salt spray (NSS)

tested (ISO 9227) shall show no more than 5 %

white corrosion products after 144 h and no base

metal corrosion (red rust) after 480 h exposure on

significant surfaces.

3.1.4.1.1 For normal production, processes that are

in statistical process control shall yield parts that are

capable of meeting the same salt spray requirements.

3.1.4.1.2 A periodic NNS test of the parts being pro-

cessed on each line running this coating shall be con-

ducted using sample size of 3 pieces minimum per

line per shift.

3.1.4.1.3 Actual processing control checks shall be

made and recorded based on chemical manufac-

turer’s instructions.

3.1.4.1.4 Significant surfaces for test evaluation of

fasteners include but are not limited to the fastener

head, socket recess and sems washer and external

surface of nut.

3.1.4.1.5 Temperature Resistance. After heating

the parts for 3 h at 150

C (part temperature) the cor-

rosion resistance requirements as specified in 3.1.4.1

shall still be met. This test requirement is only for ini-

tial approval of the finish material.

3.1.4.2 Accelerated Corrosion. The coating to this

specification shall be exposed per GM9540P, test du-

ration B (16 cycles). After exposure, there shall be no

red rust on significant surfaces. This test is required

only for initial approval of finish material.

3.1.4.3 Cathodic Protection. The cathodic protec-

tion capability of the coating can be tested by NSS

test per ISO 9227 with a specimen which is scratched

to the base metal, the scratch having a width of 0.5

mm maximum. After the 96th NSS test there shall be

no red rust in the area of the scratch. This test is re-

quired only for initial approval of finish material.

3.1.4.4 Flexibility and Chip Resistance. The coat-

ing must withstand the normal extension, flexing and

compression encountered by springs and spring clips

during product assembly, without evidence of flaking

or loss of adhesion from the base metal. It shall with-

stand normal handling and storage conditions without

chipping or flaking.

3.1.4.5 Adhesion Characteristics. Parts coated to

this specification shall show no evidence of blistering

or other appearance changes, other than a whitish

blush, after exposure to neutral salt spray test per

ISO 9227 for 96 h minimum. When tape tested per

GM9071P, 10 minutes after removal from NSS test,

there shall be no more than 3 mm peel back (peel

back adding both sides on scribed line) from the lines

scribes in an X, and no other peeling in the area under

the tape. In case of small fasteners when the surface

area of the part is not large enough to run the test will

be run on a test sample large enough to run the sam-

ple shall be test treated with the fasteners.

3.1.4.5.1 Parts shall be tested to meet the adhesion

requirements for initial approval. This test shall be

conducted on a periodic basis per the applicator’s

control plan.

3.1.4.5.2 For normal production process that are in

statistical process control shall yield parts that are ca-

pable of meeting the adhesion requirements.

3.1.4.5.3 For statistical process control the adhesion

characteristic test shall be run along with NSS test

(see 3.1.4.1).

3.1.4.6 Chemical Resistance. Coated parts in the

as received condition shall be tested against following

chemicals per the respective test methods shown.

Page 2 of 4 December 2000

GM WORLDWIDE ENGINEERING STANDARDS GMW3359

a Windshield washer solvent, 9985670 or similar if

approved by engineering (GM9509P)

b GM fabric cleaner, 9981228 or similar if approved

by engineering. (GM9509P)

c Gasoline (GM9501P).

There shall be no discoloration of the surface.

3.1.4.7 Ozone Resistance. Not applicable.

3.1.4.8 Hydrogen Embrittlement. All parts heat

treated or highly cold worked to the specified core

hardness greater than HRC 32 or surface hardness

HRC 35, which are processed through hydro-

gen generating process shall be processed per

SAE/USCAR-5.

3.1.4.9 Torque-Tension. Metric threaded fasteners

M6 and larger shall be subject to torque-tension mon-

itoring through the use of surrogate M10 × 1.5 test

bolts. Ten surrogate bolts shall be processed with the

production parts. A minimum of 10 bolts per finish line

per shift shall be monitored per SAE/USCAR-11, ex-

cept tightening speed shall be (30 ± 3) RPM. The six

(6) sigma torque range value must be within the listed

range (Table 2). The test results shall be maintained

in file to be submitted when required.

Thread Size Surrogate

bolt Part

number

Test Nut part

number

Test Washer

Part Number

Torque (Nm) Tension (kN)

Coefficient

of Friction

M10 × 1.5

11516105 11516090 11502644 48 ± 8 28.3 0.13 ± 0.03

3.1.4.10 Coefficient of Friction. The coefficient of

friction of threaded fasteners shall be (0.13 ± 0.03)

(six sigma values) when tested per DIN946 with the

following exceptions:

• Tightening speed shall be 30 ± 3 RPM

• Test samples (excluding driven fasteners) shall be

thoroughly cleaned with an appropriate fluid/chem-

ical to remove any grease/oil/wax/other contami-

nants.

• Test clamping force shall be calculated as 75 % of

proof load.

Note: Torque-Tension Test and Coefficient of Friction

Tests are required for the initial approval of the finish

material. Suppliers/Applicators can run either Torque-

Tension Test or Coefficient of Friction Test for quality

control.

3.1.4.11 Bearing Surface Characteristics. M10

heavy hex flange bolts (parts number 11900193

or equivalent) shall be tested per SAE/USCAR 11

with the following requirements: Tightening speed

shall be (30 ± 3) RPM. Test nut shall be 11516090.

Tension load shall be 24 kN. Test shall be conducted

with ELPO coated test washers (11515490 except

unhardened and coated with 9984094, medium build

ELPO) and aluminum test washers (3.0 mm minimum

thick, 10.25-10.50 hole size, AA6063T52 aluminum).

The 6 sigma torque range shall lie within 35-52

N·m for 10 samples tested for both the ELPO and

aluminum bearing surfaces. These tests are required

for the initial approval of the finish material.

3.2 Processing Requirements. Subparagraphs

were not applicable.

3.3 Performance Requirements.

3.3.1 Chemical Requirements. Not applicable.

3.3.2 Mechanical Requirements. Not applicable.

3.3.3 Physical Requirements. Not applicable.

3.3.4 Additional Requirements. Not applicable.

3.4 Requirements on other Stages during Life Cy-

cle.

3.4.1 Chemical Requirements.

3.4.1.1 Recyclability . Parts with this coating shall

not have any negative effect on recyclability of the

parts.

3.4.1.2 Physiological Safety. The coating material

must not cause any health hazard either to line oper-

ators or customers.

3.4.2 Mechanical Requirements. Not applicable.

3.4.3 Physical Requirements. Not applicable.

3.4.4 Additional Requirements. Not applicable.

4 Manufacturing Process

Not applicable.

5 Rules and Regulations

5.1 Legal Regulations. For use of this material the

valid laws and other regulations and recommenda-

tions in the country of usage shall be followed.

5.2 Language. In the event of any conflict between

the English and domestic language regarding this

document, the English language will take prece-

dence.

December 2000 Page 3 of 4

GMW3359 GM WORLDWIDE ENGINEERING STANDARDS

5.3 Restricted and Reportable Substances for

Parts. All materials supplied to this specification

must comply with the requirements of GMW3059.,

Restricted ans Reportable Substances for Parts.

5.4 Inspection and Rejection. All shipments of ma-

terials or parts under contract or purchase order man-

ufactured to this specification shall be equivalent in

every respect to the initial samples approved by engi-

neering. There shall be no changes in formulation or

manufacturing process permitted without prior notifi-

cation and approval by engineering. Lack of notifica-

tion by the supplier constitutes grounds for rejection

of any shipment. While samples may be taken from

incoming shipments and checked for conformance to

this specification, the supplier shall accept the respon-

sibility for incoming shipments meeting this specifi-

cation without dependence upon the purchaser’s in-

spection.

5.5 Initial Source Approval. No shipments shall be

made by any supplier until representative initial pro-

duction samples have been approved by Materials

Engineering as meeting the requirements of this spec-

ification.

5.6 Safety Data Sheets. Completed copies of

the Material Safety Data Sheets (MSDS) meeting

GM information requirements, consistent with the

ISO 11014-1 standard must be submitted with any

new material submissions or where a composition

change has occurred.

6 Approved Sources

Supplier to this specification must be approved by the

respective Specialist Team/TDGs. GMNA approved

suppliers names are available on the online MATSPC

system. For other GM locations the responsible en-

gineering group should be contacted to obtain the

names of approved sources in the individual country.

7 Coding System

This material specification shall be referenced in other

documents, drawings, VTS, CTS, etc. as follows:

Test to: GMW3359

8 Release and Revisions

8.1 Release. The specification was first approved in

February 2000 and published in June 2000.

8.2 Revisions.

Rev. Date Description (Org.)

A DEC 2000 Format Revision (GMNA)

Page 4 of 4 December 2000