I'm getting pieces together from my '57 to go to the platers, both cad and zinc, and I seem to recall a post some time ago warning of not leaving zinc diecast parts in assys as the plating baths would destroy the part. Do I remember this correctly? Specifically thinking of the diecast cam in the trunk lock assy to be cad plated, but also wondering if there are any other pieces to be concerned about, door latch assys, or....? Does this apply to both zinc and cad plating? Seems like zinc parts would be OK with zinc plating. Thanks for any info.
-
-
Re: Cad / Zinc plating - C1
Rod - I'd expect the Zn and Cd plating process to be basically identical except for the metal , i.e Zn or Cd, being used as the metal to be plated. So, if the plating process/baths are different, I'd suggest working closely with the plater to make sure there are no surprizes. Pete -
Re: Cad / Zinc plating - C1
Rod - I'd expect the Zn and Cd plating process to be basically identical except for the metal , i.e Zn or Cd, being used as the metal to be plated. So, if the plating process/baths are different, I'd suggest working closely with the plater to make sure there are no surprizes. PeteComment
-
Re: Cad / Zinc plating - C1
The issue is not necessarily with the plating, but the way most platers prepare the parts for plating with zinc or cad. Most platers will remove all the old plating with acid, and the acid will disolve the pot metal parts (like the cam in tne trunk latch). Unfortunately, this cam is not avaialable anywhere, so you are left with a freshly plated paper weight!
The cam is very easy to remove (2 rivets if I remember right), so dont take the chance, remove all pot metal parts. I acid strip all the parts that I plate in my tank. I found out the hard way, that cad will contaminate a zinc plating tank and ruin the chemicals. Unfortunately, you can't really tell if a part has zinc or cad on it, so it is prudent to acid strip all parts to prevent contamination of some expensive plating bath.
Regards, John McGrawComment
-
Re: Cad / Zinc plating - C1
The issue is not necessarily with the plating, but the way most platers prepare the parts for plating with zinc or cad. Most platers will remove all the old plating with acid, and the acid will disolve the pot metal parts (like the cam in tne trunk latch). Unfortunately, this cam is not avaialable anywhere, so you are left with a freshly plated paper weight!
The cam is very easy to remove (2 rivets if I remember right), so dont take the chance, remove all pot metal parts. I acid strip all the parts that I plate in my tank. I found out the hard way, that cad will contaminate a zinc plating tank and ruin the chemicals. Unfortunately, you can't really tell if a part has zinc or cad on it, so it is prudent to acid strip all parts to prevent contamination of some expensive plating bath.
Regards, John McGrawComment
-
Re: Cad / Zinc plating - C1
Thanks to both for your responses.
John, it sounds like you may have been the original poster on this issue, as I recall similar comments regarding ending up with a lump of metal in place of an irreplaceable component. You're correct in that the cam is retained by two small rivets which will be easy enough to remove so I can save the cam. Thanks again.Comment
-
Re: Cad / Zinc plating - C1
Thanks to both for your responses.
John, it sounds like you may have been the original poster on this issue, as I recall similar comments regarding ending up with a lump of metal in place of an irreplaceable component. You're correct in that the cam is retained by two small rivets which will be easy enough to remove so I can save the cam. Thanks again.Comment
-
Cad plating is a bad idea...
When I zinc plate parts, I just bead blast and thoroughly clean the parts in preparation for plating. I remove as little material as possible with the bead blasting, and I do not even attempt to remove all of the original plating. Zinc will plate right over the original zinc plating and base metal if the part is properly prepared. Zinc will not plate over cad. I have never run into an original part that was cad plated, and I don't believe that any corvette parts were ever originally cad plated. GM specs called for zinc or cad. So given the choice, any supplier would have chosen zinc over cad.
I think cad plating is a very bad idea. It's not original, it's bad for the environment, and it's a health risk. If someone cad plates a part, and years from now someone else goes to bead blast that part unaware that it is cad; they would inhale a very dangerous material.Comment
-
Cad plating is a bad idea...
When I zinc plate parts, I just bead blast and thoroughly clean the parts in preparation for plating. I remove as little material as possible with the bead blasting, and I do not even attempt to remove all of the original plating. Zinc will plate right over the original zinc plating and base metal if the part is properly prepared. Zinc will not plate over cad. I have never run into an original part that was cad plated, and I don't believe that any corvette parts were ever originally cad plated. GM specs called for zinc or cad. So given the choice, any supplier would have chosen zinc over cad.
I think cad plating is a very bad idea. It's not original, it's bad for the environment, and it's a health risk. If someone cad plates a part, and years from now someone else goes to bead blast that part unaware that it is cad; they would inhale a very dangerous material.Comment
-
Re: Cad plating is a bad idea...
Don, I'm sorry to disagree with you, but I believe quite a few parts on the early cars, at least, were cad plated. Also have the concurring opinion of one of the most knowlegeable experts on early cars on this board. Some say it's difficult to differentiate between cad and zinc, but in my experience, I feel I can tell to some extent by the "color". It appears most of the underhood, internal door and trunk parts (excluding nuts & bolts) were cad plated. Cad is much more durable than zinc, as evidenced by a complete lack of remaining plating on what was apparently originally plated zinc (most screws, nuts, etc), while the above mentioned parts often retain some degree of the original plating, still in decent condition.
You're correct that cad is toxic, but it apparently was used extensively until we got smart and put stricter controls on its use, which increased the cost, which in turn made zinc a more cost effective option. Apparently, cad and zinc must have been roughly equivalent in cost 40-50 years ago, or GM wouldn't have spec'd "either or".
Thanks for your response.Comment
-
Re: Cad plating is a bad idea...
Don, I'm sorry to disagree with you, but I believe quite a few parts on the early cars, at least, were cad plated. Also have the concurring opinion of one of the most knowlegeable experts on early cars on this board. Some say it's difficult to differentiate between cad and zinc, but in my experience, I feel I can tell to some extent by the "color". It appears most of the underhood, internal door and trunk parts (excluding nuts & bolts) were cad plated. Cad is much more durable than zinc, as evidenced by a complete lack of remaining plating on what was apparently originally plated zinc (most screws, nuts, etc), while the above mentioned parts often retain some degree of the original plating, still in decent condition.
You're correct that cad is toxic, but it apparently was used extensively until we got smart and put stricter controls on its use, which increased the cost, which in turn made zinc a more cost effective option. Apparently, cad and zinc must have been roughly equivalent in cost 40-50 years ago, or GM wouldn't have spec'd "either or".
Thanks for your response.Comment
-
Re: Cad plating is a bad idea...
Don,
You are correct that the majority of parts were zinc znc not cad plated, but all it takes is inadvertently attempting to plate a few cad parts to contaminate the solution. Once contaminated, I have not found any way of removing the contamination. I have tried charcoal filtering and several other methods, to no avail. Throwing away the sulotion and starting fresh was the only fix. Since I have started acid stripping all my parts, I have had no contamination problems. The indication of the problem manifests itself by little black blisters forming under the zinc plate after a few hours to several days later. I have a fairly large tank, and it breaks my heart to have to dispose of this expensive solution.
Cad has superior corrosion protection capabilities, and is the only plating approved for many critical aircraft components. The few things that I want cad plated are done by my local propeller repair facility. All my radio cases get cad plated because cad can be soldered to very easily. It is almost impossible to solder to a zinc plated part. Both zinc and cad can be dipped in a chromate solution whis imparts the slight gold color common to many parts. The chromate forms a zinc (or cad) dichromate shell over the plated part to increase corrosion resistance.
Regards, John McGrawComment
-
Re: Cad plating is a bad idea...
Don,
You are correct that the majority of parts were zinc znc not cad plated, but all it takes is inadvertently attempting to plate a few cad parts to contaminate the solution. Once contaminated, I have not found any way of removing the contamination. I have tried charcoal filtering and several other methods, to no avail. Throwing away the sulotion and starting fresh was the only fix. Since I have started acid stripping all my parts, I have had no contamination problems. The indication of the problem manifests itself by little black blisters forming under the zinc plate after a few hours to several days later. I have a fairly large tank, and it breaks my heart to have to dispose of this expensive solution.
Cad has superior corrosion protection capabilities, and is the only plating approved for many critical aircraft components. The few things that I want cad plated are done by my local propeller repair facility. All my radio cases get cad plated because cad can be soldered to very easily. It is almost impossible to solder to a zinc plated part. Both zinc and cad can be dipped in a chromate solution whis imparts the slight gold color common to many parts. The chromate forms a zinc (or cad) dichromate shell over the plated part to increase corrosion resistance.
Regards, John McGrawComment
-
Re: Cad plating is a bad idea...
I have plated many many corvette parts and have never run into cad. A few have been C1 parts but the vast majority have been C2-C3. So, I don't discount the possibility of cad especially on early cars, but I remain skeptical.
I agree that Cad is more durable and may have other advantages, but it's just not worth the health risk. Especially for the unwitting person who goes to bead blast those parts in the future. Zinc is more likely to be correct and is very difficult if not impossible to differentiate from cad. These cars no longer encounter inclimate weather so the corrsion resistance of zinc should be more than adequate. Any benefits from cad do not outweigh the risks. I just think it is irresponsible to put future owners/restorers at risk for very little benefit. Just my opinion.Comment
-
Re: Cad plating is a bad idea...
I have plated many many corvette parts and have never run into cad. A few have been C1 parts but the vast majority have been C2-C3. So, I don't discount the possibility of cad especially on early cars, but I remain skeptical.
I agree that Cad is more durable and may have other advantages, but it's just not worth the health risk. Especially for the unwitting person who goes to bead blast those parts in the future. Zinc is more likely to be correct and is very difficult if not impossible to differentiate from cad. These cars no longer encounter inclimate weather so the corrsion resistance of zinc should be more than adequate. Any benefits from cad do not outweigh the risks. I just think it is irresponsible to put future owners/restorers at risk for very little benefit. Just my opinion.Comment
Comment