F1136 specification covers the basic requirements for
water-based zinc/aluminum dispersion inorganic basecoats and
optional sealers and topcoats for fasteners. The basecoat can
contain chrome (C) or be non-chrome (NC).
These coatings are applied by conventional dip-spin, dip-drain, or spray methods to ferrous parts which
can be handled through a cleaning, coating, and baking operation, and which are not adversely affected
by baking temperatures up to 626°F.
The coating process does not induce the possibility of internal hydrogen embrittlement providing that
the fasteners have not been cleaned or pre-treated with an acid or phosphate. Alkaline cleaning or vapor
degreasing is required along with shot blasting to remove rust or scale.
These coatings are classified into six grades according to the requirements in Below Table.
Grade 1 requires a minimum basecoat thickness of 0.16 mil (0.052 oz/ft2). This is usually applied in two
coats to bulk parts, or one coat to racked parts. No topcoat is applied in Grade 1.
Grade 2 requires a minimum basecoat thickness of 0.20 mil (0.066 oz/ft2). This is usually applied in two
coats to bulk parts, or one coat to racked parts. No topcoat is applied in Grade 2.
Grade 3 requires a minimum basecoat thickness of 0.20 mil (0.066 oz/ft2) and a single coat of the clear
sealer. The sealer provides additional corrosion protection and greater lubricity than Grade 2.
Grade 4 requires a minimum basecoat thickness of 0.31 mil (0.092 oz/ft2). This is usually applied in
three coats to bulk parts, or one to two coats to racked parts. No topcoat is applied in Grade 4.
Grade 5 requires a minimum basecoat thickness of 0.20 mil (0.066 oz/ft2) and a single coat of the
lubricated sealer. The sealer provides additional corrosion protection than Grade 2 and greater
lubricity than Grade 3.
Grade 6 requires a minimum basecoat thickness of 0.20 mil (0.066 oz/ft2) with various pigmented topcoats
applied. The topcoats can be black or various other colors.
Orders for parts under this specification shall include the following information:
1. Quantity of parts
2. Grade of coating as given in Below Table,
3. Specify chrome (C) or non-chrome (NC). Unless otherwise specified, coating to this specification will
be supplied with chrome,
4. For Grade 6, specify the type of topcoat (that is, Grade 6; Black, Type X), and
5. Any additions to the specification as agreed upon vbetween the purchaser and the supplier.
| Grade No. | Topcoats Type | Coating Thickness Average (mil) | Coating Weight Average(oz/ft2) | Minimum SST Hours (h) | |
|---|---|---|---|---|---|
| (C) | (NC) | ||||
| 1 | None | 0.16 to 0.20 | 0.052 to 0.066 | 240 | ... |
| 2 | None | 0.20 to 0.31 | 0.066 to 0.092 | 500 | 240 |
| 3 | Clear Sealer | 0.24 to 0.47 | 0.072 to 0.111 | 1000 | 720 |
| 4 | None | 0.31 to 0.59 | 0.092 to 0.164 | 1000 | 500 |
| 5 | Lubricated Sealer | 0.24 to 0.47 | 0.072 to 0.111 | 1000 | 720 |
| 6 | Pigmented Topcoats | 0.31 to 0.59 | 0.075 to 0.131 | 500 | 500 |
Appearance—The coating shall have a uniform appearance free from tears and other discontinuities which
may affect the appearance or performance of the coating, or both.
Adhesion—The coating shall show less than 5 % removal following the tape adhesion test. Due to the
nature of the coating, some removal is expected, but removal of the coating to expose the substrate
indicates poor adhesion and is cause for rejection.
Corrosion Resistance—The coating shall be capable of withstanding exposure to salt spray test (SST) for
the minimum hours (h) specified in Below Table. Unless otherwise defined, acceptable corrosion
resistance
shall be Rust Grade 6 or higher (see Test Method D610 for definition) on significant surfaces(see
Terminology F1789 for definition).
Blisters—There shall be no signs of blisters after testing in accordance with 6.1.
Thread Fit—The coating shall not have an adverse effect on normal installation and removal practices as
determined by the proper GO thread gage.
The thickness of the coating is limited by the basic thread size (3A GO gage for external threads, 2B GO
gage for internal threads). Where greater thickness is necessary, the internal threads may be produced
oversized (before coating) providing the finished product (after coating) meets all the specified
mechanical properties. Where mechanical properties are not specified, oversizing is subject to the
approval of the purchaser.
Hydrogen Embrittlement—When specified in the purchase order, the applicator shall certify that the
process did not expose the parts to acid or phosphating to guarantee the absence of internal hydrogen
embrittlement.
Corrosion—Corrosion resistance shall be tested in accordance with Practice
B117 followed by Test Method D610 to rate the amount of
corrosion.
Coating Thickness—The coating thickness shall be determined by magnetic induction, X-ray fluorescence
spectroscopy, microscopic examination of a cross-section taken perpendicular to the significant
surfaces, or weigh-strip-weigh method. When using magnetic induction, or X-ray fluorescence, an average
of ten measurements on the flat surface of one part shall be used.
NOTE 1—The weigh-strip-weigh method involves weighing the test specimen before and after the coating is
stripped. The method requires a reagent that does not attack the base metal (for example, 20 %
NaOH).
Adhesion—Adhesion of the coating shall be tested in accordance with Test Methods
D3359 Scribe-Grid Test, where practical. Determination if
base material is exposed may be done by visually inspecting the part, or exposing the part to salt spray
test (see Practice B117 ) for 96 h and observing if red rust occurs.
Hydrogen Embrittlement—When specified in the purchase order, testing shall be conducted in accordance
with Test Methods F606 or
F1940.
When requested by the purchaser, samples shall be acquired in accordance with Guide F1470.
Materials that fail to conform to the requirements of this specification shall be rejected.
aluminum; chrome; coating; corrosion; dip spin; fasteners; protection; resistance; rust; sealer; zinc
ASTM Standards:
B117 Practice for Operating Salt Spray (Fog)
Apparatus.
D610 Test Method for Evaluating Degree of Rusting on Painted Steel
Surfaces.
D3359 Test Methods for Measuring Adhesion by Tape
Test.
F606 Test Methods for Determining the Mechanical Properties
of Externally
and Internally Threaded Fasteners, Washers, and Rivets.
F1470 Guide for Fastener Sampling for Specified Mechanical
Properties and
Performance Inspection.
F1789 Terminology for F16 Mechanical Fasteners.