ASTM B Type II and III zinc chromate plating Q&A’s. *Note: Answer is based upon pre versions of B (, , ). The revision. Hi, can anyone advise if the ASTM std ASTM B [link by ed. to spec at TechStreet] std specification for Electroplated coatings on Iron and steel, the . ASTM Be1 Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel Scope This specification covers requirements .
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Put the chromate on light. III zinc plating A discussion started in but continuing through Q. We are getting poor coverage on the as-cast surface of some steel castings using a yellow Zinc chromate.
ASTM B633-98 std: Electrodeposited coating of Zinc
Don Atm – Elkhart, Indiana. Sorry, but if you need one particular look, you must go through the ugly process of maintaining sample boards with acceptable vs. Also, some yellow chromates are clear w. Numeral indicates thickness in micrometers. Until a very few years ago chromate conversion coatings were based on hexavalent chromium, and deposited a thick film that was relatively easy to dye. So if you need to color match, you need to do it with a requirement for compliance with sample parts — not a verbal description.
ASTM B std: Electrodeposited coating of Zinc
ASTM B and all other worldwide standards were written around the time when no one spoke about trivalent. They share, however, the most basic of metal finishing requirements: I need to specify platings that do not contain Hexavalent Chromium for parts that will be used in the automotive industry.
I’ve seen this done less commonly on chromated zinc plating than on chromated aluminum.
A Iron or steel with zinc electroplate. A heavy chromate will shear under paint and cause the paint to peel. What process variation would produce these different results?
The problem may not be with the chromate at all. How do you know if it is supposed to be Zinc Yellow or Zinc Clear? The Standard default is gold for type II coatings unless otherwise specified. All information presented is for general reference and does not represent a professional opinion nor the policy of an author’s employer.
Please forgive any resultant repetition or failures of chronological order.
ASTM B-633 Type II vs. III zinc plating
Certain castings are difficult, if not impossible, to plate in either cyanide or alkaline non-cyanide plating baths. Zinc bb633-98 is usually considered a functional coating, not a decorative one. You can get the same finish only for blue and black hex chrome with tri substitutes, but not for yellow or olive as of yet.
Yellow chromate should get 96 hrs to failure. Zinc plated components vary from one industry to another. Rest in peace, Ken. Can anyone give me some direction on how to get the customer to accept going to clear. High strength steels tensile strength greater than MPa shall not be electroplated. Also, I found out that the casting is painted after plating.
Zinc Plating: ASTM B Type II vs. III
Surfaces to be painted should be ONLY lightly chromated. It would be “bright, blue” — that is, shiny and metallic but with a bluish rather than a yellowish cast.
I will be attending the ASTM B8 committee meetings in Philly later wstm week and will mention this letter to the sub-committee chair responsible for the B spec. From beautiful Pine Beach New Jersey: Hi, I recently received 2 batches of parts from two separate platers using this specification. SC 4 very severe. Ken Vlach – Goleta, California.
No it does not imply that. The end user must decide when a part fails, at “white rust” corrosion the chromate has failed or red rust both the chromate and the zinc are gone exposing the base metal. In 24 years I have only been asked this question once before and I presume it involves phosphating over zinc plating for those heavy phosphating grammage applications, where normal phosphating will not provide enough zinc phosphate that is required in the deposit.
Type II chromates are more commonly used where greater corrosion resistance is required, e. Some of today’s proprietary trivalent chromium coatings are very thin and consequently will not generate a highly saturated color though.