ASTM B Type II and III zinc chromate plating Q&A’s. greater corrosion resistance is required, e.g., for SC3 & SC4 (13 & 25 microns zinc, respectively). Blue/Zinc. Blue/Zinc. Yellow/Zinc. Yellow/Zinc. ASTM B Type II SC 3 (FE/ZN 13). Type II SC 2 (FE/ZN 8). Type II SC 1 (FE/ZN 5). Type III SC 3(FE/ZN 13). ASTM A/AM Low and Intermediate Tensile Strength Carbon Steel Plates .. ASTM B Electrodeposited Coatings of Zinc on Iron and Steel.
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Did you ever get the answers you were looking for? This is not considered a decorative finish and will not generate matching parts. Regarding the question asked in letter ; Type II zinc plating vs.
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.
He passed away May 14, We are getting poor coverage on the as-cast surface of some steel castings using a yellow Zinc chromate. The Zinc coating on the steel does not last shiny for long, and so a further thick layer coating is added, called passivation. The Standard default is gold for type II coatings unless otherwise specified. Is there any colour difference OR is there any Salt spray difference?
Perhaps some confusion with Service Condition SC 2 moderatewhich indicates a minimum zinc thickness of 8 microns and is commonly clear chromated Type III. Different brands of chromate conversion chemistry, possibly different plating processes acid zinc vs. To minimize your searching efforts and to offer multiple viewpoints, we’ve combined some threads into the dialog you’re viewing. Our Zinc coating is carried out according to: Obviously, this must be clarified by the customer.
It still will have Hex Chrome.
ASTM B-633 Type II vs. III zinc plating
III is colorless and not expected to hold up atm long as the colored II. I will be attending the ASTM B8 committee meetings in Philly later this week and will mention this letter to the sub-committee chair responsible for the B spec. I’m not a zinc plater, but ‘Type II Clear’ seems self-contradictory. To calculate it is very difficult, as the plating is a few molecules thick.
Also, I found out that the casting is painted after plating. Don Penzenik – Elkhart, Indiana. 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 asttm provide enough zinc phosphate that is required in the deposit.
Surfaces to be painted should be ONLY lightly chromated.
ASTM B – 13 Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel
No, other colors may not be available if my presumption is right. Electrical charasteristics As much as the last layer of the passivation is thin the electrical resistivity is low. Olive green passivation is a chromate passivation in a green hue that gives excellent corrosion resistance ability hours in a salt spray test and is a good base for paint.
I need to specify platings that do not contain Hexavalent Chromium for parts that will be used in the automotive industry. The revision addresses RoHS concerns and specifically allows non-hexavalent chromate treatments. All information presented is for general reference and does not represent a professional opinion nor the policy of an asstm employer. A heavy chromate will shear under paint and cause the paint to peel.
ASTM B – Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel
Sorry, but if you need one particular look, you must go through the ugly process of maintaining sample boards with acceptable vs. As the USA moved toward metric fasteners, for a while there was a move to dye them blue. That seems a bit discretional to me. Our plater would like to go 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. I am not getting the difference between this. Trivalent chromates give paler and lighter finishes; some use metals, some use b33, some use dyes, in order to replicate the Hex finish.
I have the exact same questions. Olive Drab aatm is hrs. The exterior visual determined according to last layer. Iron metals rust relative quickly, even in a non-corrosive environment. Going with clear will make it difficult to tell what is clear chromated zinc vs.
Type II chromates are more commonly used where greater corrosion resistance is required, e. Does plating make that big a difference knowing that it’s going to be painted also? A Blue 133 pale yellow is the best replacement for yellow as of now.
Rest in peace, Ken. Mark Hollenbeck alloys – Muskegon, Michigan A. Thank you for your hard work which the finishing world continues to benefit from. Go to main content. The above entries are somewhat dated: Our plater said that sstm would be willing to go thicker on the clear. Zinc coating with colorful chromate passivation. Zinc coating with colorless RoHS compliance passivation.