Chrome plating adhesion standards and tests
A discussion started in 2002 but continuing through 2017
Q. We have a caster that is imported and one of our prospective customers gave some samples of this caster to one of our competitors, who then subjected the caster bodies (1010 steel, chrome plated) to multiple hammer strikes (I believe with a waffle faced hammer). They told our customer that our plating exhibited very poor adhesion as compared to their casters.
Hitting caster bodies with a hammer is not a standard practice; however, we need to diffuse this issue with our customer and would like to establish a chrome adhesion quality specification with our overseas supplier, but I can't seem to find a spec on the internet and our local chrome plater doesn't use one.
Is there any Chrome Plating Adhesion standard out there?
Thank you,Roy Masters
- St. Joseph, Michigan, USA
A. ASTM B571 [link by ed. to spec at TechStreet] Qualitative Adhesion Testing of Metallic Coatings includes several methods of checking adhesion.Cynthia L. Meade
- Sylvania, Ohio, USA
One standard would be to whack the caster with a waffle-faced hammer and check whether any plating peels off :-)
Sorry Roy, but I'm honestly not being facetious! In addition to ASTM and other formal adhesion standards, I've seen plating shops run every imaginable kind of ad-hoc adhesion test, from bending to chiseling to grinding to crushing in a vice to baking. The fact is, your plating should stick as well as your competitor's, and your problem is not so much that your customers are being swayed by an invalid test, but that as of right now your competitor is apparently either doing a better job of getting plating adhesion than you, or is using harder steel that isn't denting and pulling away from the plating. If you pick a different adhesion test, they'll almost surely win that one too.
Specify a waffle style, the weight of hammer, and maybe a height of drop or length of lever, and insist that your suppliers meet the performance standard your competitor meets. Best of luck.
Ted Mooney, P.E.
Pine Beach, New Jersey
July 11, 2017
Q. Can someone tell me what the proper interpretation is as to what ASTM B571 [link by ed. to spec at TechStreet] adhesion test to use for Chrome Plating. Bend till legs are parallel (without Mandrel as permitted AMS2460 [link by ed. to spec at TechStreet] Para. 3.4.2) or Bend to rupture. Does anyone know Nadcap's position on the test.Bill Milla
Quality Department - Huntington Beach, California
October 19, 2017
From my recent review of NADCAP self Audit (AC7108 Chemical Processes, and AC7108/9 Electroplating)- they do not specify HOW exactly to test adhesion or hardness or other types of periodic tests. They are looking for compliance to relevant specs.
About the test method - both main Chrome AMS specs (AMS2406 [link by ed. to spec at TechStreet] and AMS2460 [link by ed. to spec at TechStreet]) send you to ASTM B571 [link by ed. to spec at TechStreet] - Bend test without mandrel.
ASTM B571 section 3 defines Bend tests (only 2 types): paragraph 3.1- over the mandrel, paragraph 3.2 - no mandrel, repeated bending over 180degrees until failure of basis metal.
- Winnipeg, Canada
October 20, 2017
Thanks for the input Leon.
AMS specifies ASTM methods for all it's in-process testings.
Regarding Adhesion Test; the Way I see it, if Para. 3.4.2 of AMS 2460A - Chrome Plating prohibits the use of mandrell ("no mandrell") the proper test would then be para. 3.2 of ASTM B571 - bend to failure/rupture.
Para 3.1 requires a mandrel and therefore can't be used.
METAL amadeya42 - Huntington Beach
December 7, 2017
Q. So we are trying to "test" the chrome plating on nut drivers. From what I can learn there is no real defined test other than the mandrel test which is not applicable to our product. the spec's talk about an impact test using a 5 mm ball hammer with medium to heavy blows. To me that would be a pendulum swing type test. Can anyone shed some light on that sort of test? What size mass to use, from how high? Is the simple thing to see if when the chrome surface is "cracked or fractured" that it does not peel from the substrate? If the chrome cracks, how far from crack should it be adhered to substrate?Bruce Welch
- Dallas, Texas, Unites States
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