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Switching from post-plate to pre-plate
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My vendor is proposing a cost reduction of ~ $ 8.00 to the power supply Tray used in our unit. This will consist of changing the material from a post-plated material to a pre-plated material.
What difference that will make in term of material quality and performance?
Thanks.
Cliff B [last name deleted for privacy by Editor]--
Hi, Cliff. Normally, the cost advantages of preplating accrue from the fact that the raw material is plated as a continuous strip. The downside is that when you shear pieces out of this, or put holes in it, there will be no plating on the edges.
If you are doing nickel plating, rarely will an unplated steel edge be a satisfactory finish unless you can roll it under to keep it away from the elements. If you are zinc plating, it may well be fine, since zinc is sacrificial to steel and can protect it to some extent even where the steel is not covered. Good luck.
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 Ted Mooney, P.E. finishing.com Brick, New Jersey |
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Hi Cliff,
It would be extremely helpful to us if you informed us of the materials of construction and the plated materials. In addition to sheared edges, if the material is to be worked in a forming operation the plating may crack and delaminate as well, unless the deposition process has been specifically tuned for a workable deposit. Electronics mfg runs into this as pre-plated IC leads must survive trim & form operations.
Regards,
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Dave Kinghorn |
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We have been stamping pre-plated tin/on steel for the consumer electronics industries for years and have never had a problem with cracks or delaminations.
M. DAVID--
I have spoken with mechanical engineers and designing for many electronics OEM's, and there is definitely a trend toward using preplated material.........PCs and other chassis are now frequently made from preplate.......the exposed steel on the sheared edges is not a problem to them. I am talking about companies like HP etc.
Regards,
Pat Kelly- Danboro, Pennsylvania
The folks above are using preplate, so I guess that answers the question of whether it is feasible 
But it still depends on the environment and the plating material. Zinc is sacrificial, and protects steel despite the exposed edges; plus, most PCs are exposed to very benign environments.
Using a non-sacrificial plating with exposed edges in a less benign atmosphere is a problem though. As an extreme example, most plating equipment suppliers have at one time or another put their electronic controllers out on the plant floor and seen what a damp, acid-laden, environment does to them. I've seen integrated circuits actually break off the board (all 16 legs) in under 3 years in older plating shops with poor ventilation and unsealed electronic cabinets. It's a matter of specific cases.
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 Ted Mooney, P.E. finishing.com Brick, New Jersey |
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We make switch-mode power supplies for telecommunications and have always used zinc plating with chromate conversion. Recently we have discussed going to pre-plated steel. Does anyone know exactly what kind of pre-plate the Personal Computer manufacturer's are using. From what we can tell it looks like it would do the job for us. Is it as good as zinc chromate for corrosion protection? Any responses would be appreciated.
Thanks,
Peter Stern- Burnaby, BC, Canada
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I represent the United States largest producer of preplated strip products. We supply a wide range of pre-plated nickel and zinc products into the automotive, electrical, computer, household, and office equipment markets. Not every application can be switched to preplated, but a great deal of them CAN and DO.
Mike Hartmansteel strip - Warren, Ohio
December 18, 2008
I am investigating the use of pre-tinned amp clips for making an electrical connection. Currently we use post-tinned clips. I have read that often materials are post-tinned to prevent corrosion. Would that be the same reason with CuZn 30? Thank you.
Brandt WillinghamProduct Engineer - Fresno, California
February 23, 2010
My company designs and manufactures electronic equipment for the television broadcast and post production industries. The rack mounted frames I design were once CRS, zinc plated, then masked and painted (powder coat). Since about 7-8 years ago, I heard of more usage with pre-galvanized steel sheet (GalXC from USS Posco in Pittsburgh, CA) from companies like HP and decided to give it a try. We were mainly a domestic company and never saw a problem with the material in the controlled studio environments our products occupy. But every so often we would have a demo unit come back after much travel mileage and we would see the white rust on the brake marks of bent flanges and even finger prints that white rusted as well. Things got worse with units that traveled internationally, especially Asia. Those units even showed red rust on the exposed sheared edges and punches. Since, our products have gone international and I am obviously concerned with using unfinished pre-zinc plated steel. I have even seen impact to the metal just while sitting in their shipping crates waiting delivery from a shipping dock. As I mentioned before, someone who handled the product with perhaps high acidic sweat(?) on their hand and fingers produced accelerated white rust. I hand delivered 2 frames back to USS Posco to show how extensive these particular units degraded. They sent them away for some chemical analysis and it was determined the white rust, particularly the hand and finger prints, were caused by some form of caustic or acidic substance, perhaps a cleaner of some sort. I am investigating my options, whether it is chromating (trivalent) the GalXC, chromating then powder coat, or go back to CRS and zinc plate after fabrication. The problem with post zinc is the cosmetic inconsistency. Cost savings dictated the change to GalXC and the alternatives to further protect it will add cost. I would like to hear if anyone is on a reverse decision from using unfinished prezinc steel.
Dan ReiswigMechanical Engineer - Grass Valley, California
March 17, 2010
I've had numerous experiences with conversion from post-plating to pre-plate . . . as an engineering manager at HP and Eaton . . . and as VP/Dir of Engineering at 3 metal fabricating companies . . . now managing projects at a manufacturer of medical products.
Post plating is a big headache to the fabricator. Most have to send parts outside for plating. They have to be counted, packaged, shipped, tracked, expedited, recounted on return, detrashed, and often put back into the production process. Parts get lost and damaged. It is expensive, problem prone, and adds one week to inventories and lead times. Your fabricator does NOT like doing this for you.
In the 1990's, ASTM A591 (now
ASTM A879 [link is to spec at TechStreet] ) electrogalvanized steel became popular for electronics equipment. It has a very thin zinc coating. The appearance was much better than the "garbage can" look of hot dip galvanized steel.
In recent years, the appearance of
ASTM A653 [link is to spec at TechStreet] has improved dramatically. It now commonly has a smooth, spangle-free appearance. Its zinc coating is several times the thickness of electrogalvanized, which translates into improved corrosion protection.
Punched and sheared edges will be exposed steel. A small amount of zinc tends to be smeared across the edge. Galvanic action causes zinc to partially protect bare steel in near proximity. Edges may show discoloration (rust) over time, but is usually minimal.
Post plating offers the benefit of depositing zinc on the edges of the part. However, it can bring a host of other problems. Many process variables in the plating process offer opportunities for defects. Plating can look bad or simply peel off. If you can find a good plater with reliable delivery, pay him well.
As a fabricator, I was presented with many designs from high tech customers. Over time I learned that whenever the customer specified Zinc & yellow chromate, it meant the customer had abandoned continuing engineering of the product or was technologically uncompetitive. Zinc & yellow chromate came to mean "old technology" and "dinosaur".
Certainly, your design will be the major factor in deciding how to coat your product. Be very careful that you don't choose post-plating because "that's the way we've always done it." . . . or "our customers expect it." That's not true anymore.
- Watertown, Wisconsin
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March 17, 2010
Thanks for the great update, Mark. The one thing I would take issue with is a prejudice against zinc plating plus chromating. What with RoHS, etc., almost no shop in the world is using the zinc plating and chromating technology they were using even five years ago, so this is certainly not "old" technology. Rather, zinc simply remains the least expensive plating process. If the driving force behind the widespread switch to preplating is cost reduction, it hardly seems fair to criticize post platers for not moving, for no reason at all, towards a more expensive finish :-) But, yes, a plating shop which is doing alloy plating like zinc-cobalt, zinc-iron, zinc-nickel, or tin-zinc has at least taken the first step away from the "commodity" market, and will probably be better off for it. Thanks and Regards,
February 10, 2010 We are a thermal printer manufacturer. We build desk top printers as well as OEM mechanisms and kiosk mechanisms. We have been using preplated material for years with very good success. We use a galvannealed material that has a higher zinc content. We would prefer to use what the Japanese use if I could figure it out. It is a lighter gray color and appears to have an anti fingerprint coating on it. I have been told that this coating is acrylic and increases the shear edge protection. I don't know. I want to be competitive with products from around the world and in order to do so, I want their material. BTW the cost reductions that have been mentioned are conservative. David Dezse-Lewis Center, Ohio, USA April 13, 2011 This is a question along the lines of the pre-plate vs post plate scenario. WE know the pre-plate is cost effective but how do they compare in terms of conductivity? Our company is potentially making some changes from post plate to preplate material but I am unaware of the differences in conductivity of the two processes. Am I going to have EMI issues as a result of the switch with everything else being equal? Corey Brenner- Colorado Springs, Colorado |