| Specification & Callouts | Description | Required Testing |
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MIL-DTL-45204
Gold Plating Type I, Grade A Type I, Grade B Type I, Grade C Type I, Grade D Type II, Grade A Type II, Grade B Type II, Grade C Type II, Grade D Type III, Grade A Type III, Grade B Type III, Grade C Type III, Grade D Class 00 Class 0 Class 1 Class 2 Class 3 Class 4 Class 5 Class 6 |
99.7% pure, less than 90 HK25 99.7% pure, 91-129 HK25 99.7% pure, 130-200 HK25 99.7% pure, greater than 200 HK25 99.0% pure, less than 90 HK25 99.0% pure, 91-129 HK25 99.0% pure, 130-200 HK25 99.0% pure, greater than 200 HK25 99.9% pure, less than 90 HK25 99.9% pure, 91-129 HK25 99.9% pure, 130-200 HK25 99.9% pure, greater than 200 HK25 20 µin 30 µin 50 µin 100 µin 200 µin 300 µin 500 µin 1500 µin include Class and thickness on print |
MIL-G-45204C was reinstated as of June 2007 after being temporarily superseded by AMS2422 and/or ASTM B488. MIL-DTL-45204 then superseded MIL-G-45204. MIL-DTL-45204D is the active revision. If you are familiar with MIL-G-45204, and you are considering plating to MIL-DTL-45204, note that ¶ 4.4.3.1.1.2 requires hardness specimens to be plated and tests to be done monthly for a stable process and weekly to prove stability. Note that MIL-STD-105 sampling has been replaced with MIL-STD-1916. Also read ¶ 3.4 for newer restrictions on strikes and underplating. The appendices of the ASTM B488 specification have more background information on the function of the various types of underplating. For the normal specification of "Gold Plate per MIL-DTL-45204" or "Gold Plate per MIL-G-45204" for all types and grades, nickel underplate is used as a diffusion barrier when plating copper or copper alloys, since gold will readily diffuse into copper. If your application will be negatively impacted by the reduced electrical conductivity of nickel or the magnetic properties of nickel, you should specify, on print or purchase order, that nickel underplating should not be used, and you should ensure that the gold thickness will be sufficient for your application. A typical print note would read "Gold Plate per MIL-G-45204 Type III, Grade A - NO nickel underplate". If your basis material is copper or a copper alloy, it does not hurt to specifically request the nickel underplate (e.g. "Gold Plate per MIL-G-45204 Type I, Grade C - WITH nickel underplate". These are not decisions that should be left to a plating shop. Our table lists all combinations of Type and Grade; although it is quite difficult to achieve some of them. Normally cobalt and/or nickel is used to harden the plating to achieve the Grade C or D hardness, and it is very difficult to simultaneously achieve the 99.9% purity with the Grade C or D hardness; although, there are some sulfite-based commercial chemistries able to achieve Type III, Grade C using arsenous acid to brighten and harden the deposit. Normally the Type III (Grade A) gold is plated from a cyanide bath. The common callouts are "Gold Plate per MIL-DTL-45204 Type I, Grade C" for alloyed, hard gold and "Gold Plate per MIL-DTL-45204 Type III, Grade A" for pure, soft gold. Neither the ASTM B488 nor the MIL-DTL-45204 specifications list bath impurities; however, we have listed them because they are crucial to successful plating results. If bath impurities are not tested and controlled, the shop will eventually fail the periodic purity tests and will then be in a recall situation. Bath Testing none specified Coupon Testing - monthly ¶ 4.4.3: plate purity ¶ 4.4.3.1.1: plate hardness Coupon/Part Testing - per lot ¶ 4.4.3: coating thickness ¶ 4.4.3: adhesion ¶ 4.4.3: heat resistance ¶ 4.4.3: solderability ¶ 4.4.3: embrittlement - if specified by contract Impurities - recommended bi-weekly to maintain soft gold purity Note: Co or Ni may be hardener < 10 ppm Pb< 20 ppm Cr< 20 ppm Co< 30 ppm Cu< 50 ppm Fe< 100 ppm Ni |
| ASTM B488 Gold Plating Type I, Code A Type I, Code B Type I, Code C Type I, Code D Type II, Code A Type II, Code B Type II, Code C Type II, Code D Type III, Code A Type III, Code B Type III, Code C Type III, Code D Class 0.25 Class 0.5 Class 0.75 Class 1.0 Class 1.25 Class 2.5 Class 5.0 |
99.7% pure, less than 90 HK25 99.7% pure, 91-129 HK25 99.7% pure, 130-200 HK25 99.7% pure, greater than 200 HK25 99.0% pure, less than 90 HK25 99.0% pure, 91-129 HK25 99.0% pure, 130-200 HK25 99.0% pure, greater than 200 HK25 99.9% pure, less than 90 HK25 99.9% pure, 91-129 HK25 99.9% pure, 130-200 HK25 99.9% pure, greater than 200 HK25 0.25 µm (9.84 µin) 0.5 µm (19.67 µin) 0.75 µm (29.53 µin) 1.0 µm (39.37 µin) 1.25 µm (49.21 µin) 2.5 µm (98.43 µin) 5.0 µm (196.85 µin) |
ASTM B488-01(2006) is available from ASTM. There was a time when the ASTM B488 Type and Code call outs did not align with the MIL-G-45204 call outs, and plating shops should be very careful to ensure that a print calling for Gold Plate per ASTM B488 Type III Code A is really asking for 99.9% gold, since Type 1 Code A was the 99.9% gold call out for quite some time before ASTM decided to change back to the old specifications. The other common callout is Gold Plate per ASTM B488 Type I Code C for alloyed, hard gold, and this call out was Type 3 Code C in the ASTM B488-95 specification. Similar confusion exists in the hardness callouts: the B488-95 specification used a wider range for Code B (90-200 HK25), while the B488-01 specification has Code B for 130-200 HK25, which aligns with MIL-G-45204 Grade B. Check the notes on MIL-G-45204 for more general information on gold plating. Bath Testing ¶ 8.1: processor to use SPC ¶ X5.3.3: bath must be kept in spec by regular additions and/or analysis and additions Coupon Testing - periodic ¶ X5.3.4: plate purity ¶ X5.3.4: plate hardness Coupon/Part Testing - per lot ¶ X5.3.4: coating thickness ¶ X5.3.4: porosity Impurities - bi-weekly to maintain soft gold purity Note: Co or Ni may be hardener < 10 ppm Pb< 20 ppm Cr< 20 ppm Co< 30 ppm Cu< 50 ppm Fe< 100 ppm Ni |
| AMS2422 Gold Plating |
plating thickness to be specified on print but not less than 50 µin plate purity > 99.0% (Type I, II or III is OK) (Grade A, B, C or D is OK) |
AMS2422E is the current revision available from SAE International. AMS2422 specifies a minimum plate purity of 99.0%, and therefore allows plating of any Mil-Spec type from Type I, Grade D to Type III, Grade A. So, if you don’t care whether the gold is hard or soft, pure or alloyed, this spec should cover your needs. The solderability test is seems to be the only place where the specification may be a bit more rigorous than the Mil-Spec; other than that, it doesn’t add much to the state of the art. Bath Testing ¶ 4.4.3: processor to specify frequency and analysis methods and establish periodic test plan Coupon Testing - periodic ¶ 3.4.4: plate purity ¶ 3.4.5: corrosion resistance Coupon/Part Testing - per lot ¶ 3.4.1: coating thickness ¶ 3.4.2: adhesion bend test ¶ 3.4.3: solderability test |
| MIL-R-46085 Rhodium Plating Class 1 Class 2 Class 3 Class 4 Class 5 |
minimum 2 µin minimum 10 µin minimum 20 µin minimum 100 µin minimum 250 µin |
MIL-R-46085B is the current revision. Bath Testing no bath parameters or tests mentioned in specification Coupon Testing - periodic no periodic coupon tests mentioned in specification Coupon/Part Testing - per lot ¶ 4.5.1: coating thickness ¶ 4.5.2: adhesion ¶ 4.4.3: reflectivity ¶ 4.4.4: embrittlement |
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FED QQ-S-365 Silver Plating Type I, Grade A Type I, Grade B Type II, Grade A Type II, Grade B Type III, Grade A Type III, Grade B |
matte finish, chromate matte finish, as-plated semi-bright, chromate semi-bright, as-plated bright, chromate bright, as-plated note: newer specifications switch Type/Grade/Class designations to be sure we are paying attention |
The QQ-S-365 specification was cancelled at QQ-S-365D revision, but any silver shop should know the spec, and machine shops should pay attention to the Intended Use section when machining threaded fasteners. Unfortunately, the superseding ASTM B700 spec did not follow the same reference call outs. Silver Plate per QQ-S-365 Type I Grade A/B is a matte finish, Silver Plate per QQ-S-365 Type II Grade A/B is a semi-bright finish, and Silver Plate per QQ-S-365 Type III Grade A/B is a bright finish. The Grade is used to specify chromate anti-tarnish post-plating. The ASTM B700 uses the Type reference to specify plate purity, the Grade reference to specify the finish, and the anti-tarnish treatment is specified by the Class reference. "Type I" or "Type II" silver needs to be qualified by the referenced specification. As always, purchasing due diligence should include periodic review of bath testing and addition records. A purchaser should also review results of periodic testing, and encourage the supplier to have that testing done by an independent lab. Bath Testing ¶ 4.3.1: maintain permanent record of bath analysis/additions and job processing records Coupon Testing - periodic ¶ 4.5.6: embrittlement Coupon/Part Testing - per lot ¶ 3.4.1: coating thickness ¶ 3.4.2: adhesion ¶ 3.4.3: surface finish ¶ 3.4.4: solderability |
| ASTM B700 Silver Plating ASTM B700 Type 1, Grade A ASTM B700 Type 1, Grade B ASTM B700 Type 1, Grade C ASTM B700 Type 1, Grade D ASTM B700 Type 2, Grade A ASTM B700 Type 2, Grade B ASTM B700 Type 2, Grade C ASTM B700 Type 2, Grade D ASTM B700 Type 3, Grade A ASTM B700 Type 3, Grade B ASTM B700 Type 3, Grade C ASTM B700 Type 3, Grade D Class N Class S |
99.9% pure, matte finish 99.9% pure, bright (brighteners) 99.9% pure, bright (polished) 99.9% pure, semi-bright (brighteners) 99.0% pure, matte finish 99.0% pure, bright (brighteners) 99.0% pure, bright (polished) 99.0% pure, semi-bright (brighteners) 98.0% pure, matte finish 98.0% pure, bright (brighteners) 98.0% pure, bright (polished) 98.0% pure, semi-bright (brighteners) as-plated (no chromate) chromate finish |
ASTM B700-08 is the current revision. Beware: the older QQ-S-365 specification used the Type reference to specify the finish (matte, semi-bright, bright) and the Grade was used to specify chromate anti-tarnish post-plating. ASTM B700 uses the Type reference to specify plate purity, the Grade reference to specify the finish, and the anti-tarnish treatment is specified by the Class reference. When you mention "Type 1" silver to a plating shop, you have a 50/50 chance of communicating. The correct print note for 99.9% pure silver with no brighteners is "Silver Plate per ASTM B700 Type 1, Grade A" while the 98% pure silver without brighteners would be specified by "Silver Plate per ASTM B700 Type 3, Grade A. As always, purchasing due diligence should include periodic review of bath testing and addition records. A purchaser should also review results of periodic testing, and encourage your supplier to have that testing done by an independent lab. Bath Testing no bath parameters or tests mentioned in specification Coupon Testing - periodic ¶ 8.6: plate purity ¶ 8.7: plate hardness ¶ 8.8: reflectance ¶ 8.9: resistivity Coupon/Part Testing - per lot ¶ 8.2: coating thickness ¶ 8.3: adhesion ¶ 8.5: solderability |
| AMS2410 Silver Plating |
plating thickness to be specified on print no post-plate chromate (ASTM B700 Class N) plate purity > 99.9% (ASTM B700 Type I) |
AMS2410K is available from SAE International. The correct print note would read "Silver Plate per AMS2410". Bath Testing ¶ 4.2.2: periodic testing of cleaning and plating solutions to ensure specification conformance Coupon Testing - periodic ¶ 3.4.2: plate purity Coupon/Part Testing - per lot ¶ 3.4.1: coating thickness ¶ 3.4.3: adhesion bend test ¶ 3.5: general quality |
| AMS2411 Silver Plating high-temp |
plating thickness to be specified on print no post-plate chromate (ASTM B700 Class N) plate purity > 99.9% (ASTM B700 Type I) |
AMS2411G is the latest revision available from SAE International. A nickel underplate and post-plate heat treatment is specified. The correct print note would read "Silver Plate per AMS2411". Bath Testing ¶ 4.2.2: periodic testing of cleaning and plating solutions to ensure specification conformance Coupon Testing - periodic ¶ 3.4.2: plate purity ¶ 3.4.4: embrittlement Coupon/Part Testing - per lot ¶ 3.4.1: coating thickness ¶ 3.4.3:adhesion test after bake per ¶ 3.4.3 inspection for blisters shear or chisel test ¶ 3.5: general quality |
| AMS2412 Silver Plating copper strike |
plating thickness to be specified on print no post-plate chromate (ASTM B700 Class N) plate purity > 99.9% (ASTM B700 Type I) |
AMS2412H is the current revision available from SAE International. The copper underplate protects the base material when the silver plating is heated after plating. The correct print note would read "Silver Plate per AMS2412". Bath Testing ¶ 4.2.2: periodic testing of cleaning and plating solutions to ensure specification conformance Coupon Testing - periodic ¶ 3.4.2: plate purity ¶ 3.4.4: embrittlement Coupon/Part Testing - per lot ¶ 3.4.1: coating thickness ¶ 3.4.3:adhesion test ¶ 3.5: general quality |