ASTM B Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel. Buy ASTM B SPECIFICATION FOR ELECTRODEPOSITED COATINGS OF ZINC ON IRON AND STEEL from SAI Global. ASTM B Type II and III zinc chromate plating Q&A’s. In my opinion a Mil-C- [link is to free spec at Defense Logistics Agency, ] plating.
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We are getting poor coverage on the as-cast surface of some steel castings using a yellow Zinc chromate. Our plater would like to sstm to a clear zinc, but our customer is under the assumption that the clear will not do as good a job with corrosion resistance and salt spray life.
Can anyone give me some direction on how to get the customer to accept going to clear. Our plater said that he would be willing to go thicker on the clear.
Also, I found out that the casting is painted after plating.
ASTM B-633 Type II vs. III zinc plating
Does plating make that big a difference knowing that it’s going to be painted also? A heavy chromate will shear under paint and cause the paint to peel.
Put the chromate on light. A light yellow ast, be better than a clear. This applies to all metals. 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.
The problem may not be with the chromate at all. Going with clear will make it difficult to tell what is clear chromated zinc vs. What type of zinc plating bath is aatm plater using? Certain castings are difficult, if not impossible, to plate in either cyanide or alkaline non-cyanide plating baths. Try using an acid zinc chloride bath and see if the casting covers.
I will be attending the ASTM B8 committee meetings in Philly later this week and will mention this letter asm the sub-committee chair responsible for the B spec. The above entries are somewhat dated: To frer your searching efforts and to offer multiple viewpoints, we’ve combined some threads into the dialog you’re viewing.
Please forgive any resultant repetition or failures of chronological order. All I need to know is what color the types are.
Any information would be well received. The Standard default is gold for type II coatings unless otherwise specified. I’ve seen this done less commonly on chromated zinc plating than on chromated aluminum. I need to specify platings that do not contain Hexavalent Chromium for parts that will be used in the automotive industry. I have the exact same questions. Did you ever get the answers you were looking for?
Zinc Plating: ASTM B Type II vs. III
Does anybody know this info? Hello Claudio and Doug, My compliments for an excellent rfee of questions! The answer is Yes. ASTM B and all other worldwide standards were written around the time when no one spoke about trivalent.
It definitely implies Hex Chrome. Trivalent chromates give paler and lighter finishes; some use metals, some use permanganates, some use dyes, in order to replicate the Hex finish. You can get the same finish only for blue and black hex chrome feee tri substitutes, but not for b6633 or olive as of yet. A Blue with pale yellow is the best replacement for yellow as of now. No it does not imply that.
It still will have Hex Chrome. 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.
No, other colors may not be available if my presumption is right. To calculate g633 is very difficult, as the plating is a few molecules thick. According to RoHS the homogeneous and non-homogeneous are defined in such manner that every one may understand that the layer is removable let’s see how. What freee you say? Could you explain this? I’m not a zinc plater, but ‘Type II Clear’ seems self-contradictory. Perhaps some confusion with Service Condition SC 2 moderatewhich indicates a minimum zinc thickness of 8 microns and is commonly clear chromated Type III.
Type II chromates are more commonly used where greater corrosion resistance is required, e. Obviously, this must be clarified by the customer. Also, some yellow chromates are clear w. Answer is atsm upon pre versions of B, The revision addresses RoHS concerns and specifically allows non-hexavalent chromate treatments.
He passed away May 14, Rest in peace, Ken. Thank you for your hard work which the finishing world continues to benefit from. Regarding the question asked in letter ; Type II zinc plating vs. The part is currently being ftee in China and my local platers are suggesting a dye to get a blue color. That seems a bit discretional to me.
Is this process done in the United States, and if so by whom? To me “bright blue” does not usually literally mean “bright blue” like the sky or a robin’s egg. It would be “bright, blue” — that is, shiny and metallic but with a bluish rather than a yellowish cast.
But if you are looking for something indisputably blue, as opposed to clear with a possible slightly bluish cast, this probably requires dye. As the USA moved toward metric fasteners, for a while there was a move to dye them blue.
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. Some of today’s proprietary trivalent chromium coatings are very thin and consequently will not generate a highly saturated color though. Zinc plating is usually considered a functional coating, not a decorative one. So if you need to color match, you need to do it with a requirement for compliance with sample parts — not a verbal description.
How do you know if it is supposed to be Zinc Yellow or Zinc Clear? I am not getting the difference between this. Is there any colour difference OR is there any Salt spray difference?
Kaushik, The “Types” define supplementary finishes to be done after the plating.
II says “colored chromate coatings” meeting 96 hours of salt spray, and III says “colorless chromate conversion coatings” meeting 12 hours of salt spray. So if I’m interpreting this correct, there is both a color difference and a salt spray difference. III is colorless and not expected to hold up as long as the colored II. Hi, I recently received 2 batches of parts from two separate platers using this specification.
What process variation would produce these different results? Different brands of chromate conversion chemistry, possibly different plating processes acid zinc vs. This is not considered a decorative finish and will not b33 matching parts. Sorry, but if you need one particular look, you must go through the ugly process of maintaining sample boards with acceptable vs. It’s not possible to freee a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author’s employer.
From beautiful Pine Beach New Jersey: III zinc plating A discussion started in but continuing through Q. Mark Hollenbeck alloys – Muskegon, Michigan A.
Surfaces left-bare should be heavily chromated. Surfaces to be painted should be ONLY lightly chromated. Regards, Ted Mooney, P. Ken Vlach – Goleta, California. August 31, A. Ray Kremer Stellar Solutions, Inc. Yellow chromate should get 96 hrs to failure. Olive Drab chromate is hrs. Don Penzenik – Elkhart, Indiana.