ASTM Designation: B 700
Electrodited Coatings of Silver for Engineering Use
Surface Appearance
Grade A, Mat – Electrodeposits without luster.
Grade B, Bright – Electrodeposits obtained by the use of brighteners in the electroplating bath.
Grade C, Bright – Mechanical or chemical polishing of Grade A silver coatings.
Grade D, Semi bright – The use of addition agents in the electroplating Bath. Supplementary Surface Treatment – Specify by Class in letter code as follows:
Class N – No supplementary tarnish treatment
Class S – Supplementary tarnish treatment – not suitable for food service applications..
Silver Plating process control – Lot test
1. Solderability Test
sample size :
Test method spec: ASTM B678
Requirements :
1. Four plated sample shall be taken from each lot for each destructive test
2. Test specimen shall be suitably fluxed with non corrosive rosin flux conforming to ASTM B678 type R.2. The solder shall be alloy of 60%tin and 40% lead conforming to alloy grade 60A of ASTM B32. The temp. of solder shall be 245°±5°C
2. Adhesion Test :
sample size : 0.032- 0.064x4x1 Inch
Test method spec: ASTM B571
Requirements :
1. Specimen Shall be bent repeatedly through an angle of 180° untill fracture accures.
2 . Adhesion may be alternatively determined on by cutting the plating from the basis metal at the interface in a continuous bath and examined at 4 dia magnification to determine whether removal has be caused by the cutting away of an adherent plate or by lifting of a non adherent plate.3 An altenative adhesion test may be used , parts are heated at 150-200°C cooled in air, examined at four dia magnification for the evidence of blistering of the silvery deposit.
3. Hydrogen Embrittlement Test :
sample size : Round notched steel specimen
Test method spec:ASTM F 519Type A
Requirements :
1. specimen shall be heat treated at mi of 375±25˚F for stress relief treatment
2. The notched specimens shall be subjected to a sustained tensile load equal to 75% of the ultimate notch tensile strength of the material.
3. The specimen shall be held under load for atleast 200 hours and then examined for crack and fracture. The process shall be considered satisfactory if all specimens show no indication of cracks or failure.
Silver Plating process control – Lot test
1. Roughness Test
sample size :
Test method spec: ASNI B46.1
Requirements :
1. when the certain degree of surface roughness of the finished article is required the standards and degree of roughness shall be specified by the procuring activity in accordance with ASNI B46.1
2. measurements shall be made at several locations on each item.
3. If the number of nonconforming items equals or exceeds the rejection number for that sample, lot shall be rejected
2. Tarnish test
sample size : Test method spec:
Requirements : pipette 1ml of 20-24% ammonium sulfide in to a1 liter volumetric flask and fill it with distilled water and agitate thoroughly. place one drop of specimen on a specimen without tarnish resistant coating(grade B) and one drop on a specimen with supplementary tarnish-resistant-chromate (grade A). the drop on the grade B specimen should begin to show a black or brown color in about one minute.
3. Thickness Test :
sample size : Bars of 0.5×4 inches Test method spec:
Requirements :
1. The Coating thickness will be determined within ±10% of its true thickness.
2. The following test methods may be used as applicable: ASTM B 504,ASTM B499,X ray Spectrometry
3. The minimum Plating Thickness shall be 0.00005 inch(0.013mm) on all Surfaces on which silver is functionally necessary