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04-06-2007, 04:09 PM #1
I have a little experience getting items hard coat anodized (I've used a anodize shop and spec'd the anodize). Before I call the anodizer/plater I thought I'd ask my question here.
I have an item I'd like to make. I understand that it is recommended not to anodize threads due to unusual build up and also for galling and strength issues (hard coat anodize can crack easily and is bad for fatigue). I have seen hard anodized (HA) parts where the threaded portion was masked and later coated with Alodine. I have also seen aluminum with EN plating, which I understand is good for coating threads in aluminum as it provides lubricity and hardness to the thread.
So, my question is:
Is it possible to combine hard anodize and electroless nickel to the same part?
I understand that to do EN you must strip of any oxide layer, etch with a zinc coating, and then EN plate.
I understand that HA is an oxide layer. Could one combine the two on a single part by order of operations and careful masking? Can you mask the portion to be anodized, EN plate the other areas of the part, and then HA the area that was previously masked? Or could you mask the area for EN plating, anodize the part, then mask the HA area, and EN plate the rest?
Or is all this way to complex?
My part idea is a tube with threaded ends. The inside and threads I'd like to have EN plated for electrical conductivity and good thread wear characteristics, and the outside of the tube I would like to be HA for wear resistance.
any anodizers and platers out there?
04-06-2007, 04:23 PM #2
You can do wonders with masking and even in process machining (take off something you did not want in the finshed part).
The trouble is that if you are dealing with a vendor, it will be difficult to get done what you expect and clearly describe - in my experience.
The only successful such operation I was ever exposed to was in the plating department at Pratt & Whitney Aircraft. Here, they had exact control over every facet of what was going on - multiple steps in cleaning, masking (which included both various types of plating [for parts going to carburize] and carefully applied waxes) and preliminary, in process and final plating. Somebody had to pay for all that attention to detail. [img]smile.gif[/img]
04-06-2007, 04:45 PM #3
I guess the other gist of my question is:
Will one process "poison" the other?
For example, if I mask the area to be anodized, EN plate the rest, will I now need to mask the EN areas before anodize, or will the EN not be affected or affect the anodize process? Or will I have to now mask the EN areas to HA the rest? What if I have a sliver of EN exposed? will it screw up the anodize area or poison the tank? Or will it get removed in the process and get HA?
EN will necessitate that any oxides get removed. So should I mask the areas to be EN plated, HA the rest, and now go back and mask the andodize? And then EN plate the other areas.
So my question is, which way would require the least amount of masking and still work (if this works at all).
So, assuming I have an anodizer/plater that has the utmost attention to detail. Is anything possible in this regard, or are the two processes incompatible?
Thanks for the quick answer John, I'm not trying to be argumentative, just clarifying my question. If you have actually seen parts that have areas that are hard coat and areas that are EN plated, that might answer my question.
04-07-2007, 12:30 PM #4
A small aside:
Where did you hear that you aren't supposed to anodize threads? I've seen many examples of both type II and type III on parts with several threaded portions. I've got two parts here in front of me in type II that have 15/16"-14 and #4-40.
Is an anodized thread really that much of a problem?
To answer your question, nickel plating would "posion" the anodizing bath, and anodizing would prevent nickel plating. So both would require the same amount of masking, but anodizing first would be safer, as the only result of a bad mask would be incomplete plating, where the nickel plating in the anno bath could cause burns in the aluminum.
My biggest concern, however, would not be getting it done, but the durability of the resulting finish. At a guess, i'd say that the nickel plating would rapidly begin the chip, flake, and peel at the boundaries between it and the anno.
EDIT: Pardon me for not reading - I don't know how an electroless nickel plating job would react to the aluminum oxide. My post is referring to electroplating.
04-07-2007, 03:54 PM #5
Ive worked with aircraft repair and overhaul parts for years. Just about any process that will build up a surface Ive seen. Electroless Nickle plating can be put on aluminum but the only applications that I have seen that could be called sucessful are bores as they seem to retain the cylinder of plating. ODs and flat surfaces want to shed this stuff it seems,not always but usually. Different expansion rates etc. Normally nickle is baked out after its put on,my understanding is this hardens it. As far as hard anodize it will affect thread size (use H5 taps) but,it doesnt chip. Masking will drive up the cost of any plating job a lot. Most nickle jobs we send out for plate they plate the whole part all over,"wax" dip the part,leave the wax where we need the buildup and strip the rest off. Essentially they mask the strip,not the plating.