Zinc Plating Subframe/traiiling arms?

[jwest11]

Pulled out the rear of my car to clean things up and install new parts. I'm considering getting the subframe and trailing arms powder coated black but the cost is what is making me think about zinc plating them. I've heard about the dangers of reducing the strength but not sure how much of an effect that will actually have since out of the two methods, one uses heat and one uses electricity (i think).

Also, do most plating companies strip the part before hand in a chemical bath or powder coat or does that usually need to be done elsewhere? I'm wondering if getting the parts chemically stripped instead of sandblasted and then powder coated would be a cheaper option. Thinking about the same thing with my brake calipers.

Thanks!

[varg]

The temperatures involved in powdercoating should be too low to cause issues with most steels, at well under 300°C. Certain Aluminum alloys and treatments are where it can cause an issue. Without getting to into the details, putting the part in an oven at 200°C for a while can basically ruin the heat treatment done to the part to achieve the desired characteristics. No such issue with steels at powdercoating temperatures. Plating those big parts will be very expensive I imagine.

[jwest11]

The temperatures involved in powdercoating should be too low to cause issues with most steels, at well under 300°C. Certain Aluminum alloys and treatments are where it can cause an issue. Without getting to into the details, putting the part in an oven at 200°C for a while can basically ruin the heat treatment done to the part to achieve the desired characteristics. No such issue with steels at powdercoating temperatures. Plating those big parts will be very expensive I imagine.

It seems zinc plating and powdercoating use similar temperatures though. Does one method have the chance of changing the structural integrity of a part over the other? Do you also know whether or not one is more corrosion or durable than the other? I got quotes on powder coating and it was a lot more expensive than I anticipated, a large part of that cost is powder coating. Would a chemical dip change characteristics of a part? (im not familiar with the process so I dont know if heat is used) Seems like using the chemical method would save time and money.

[Shangsta]

It seems zinc plating and powdercoating use similar temperatures though. Does one method have the chance of changing the structural integrity of a part over the other? Do you also know whether or not one is more corrosion or durable than the other? I got quotes on powder coating and it was a lot more expensive than I anticipated, a large part of that cost is powder coating. Would a chemical dip change characteristics of a part? (im not familiar with the process so I dont know if heat is used) Seems like using the chemical method would save time and money.

Why would you zinc plate a subframe and control arms. Like Varg said i dont think it will be cheap to do parts that big. They both will be perfectly fine with powder coating and if thats too expensive then just paint them. The powder coating is going to have no ill effect on these parts and is done all the time. Powder coating will help with corrosion but if you live in an area where salt corrosion is bad then I would recommend giving the car a good underside cleaning once or twice a year to help prevention corrosion from becoming a problem.

[nando]

The real question would be, if you could afford to zinc plate such large pieces (I'm not sure it's even possible, depends on the size of available dip tanks), why would you drive your E30 in the salt where it might matter? I'd just drive a different car I don't care about (and I do).

There's a reason plating is only used on small parts and fasteners, while paint or other less expensive coatings are used elsewhere.

[varg]

It seems zinc plating and powdercoating use similar temperatures though. Does one method have the chance of changing the structural integrity of a part over the other? Do you also know whether or not one is more corrosion or durable than the other? I got quotes on powder coating and it was a lot more expensive than I anticipated, a large part of that cost is powder coating. Would a chemical dip change characteristics of a part? (im not familiar with the process so I dont know if heat is used) Seems like using the chemical method would save time and money.

The plating bath temperature will be higher than ambient but nowhere near the temperature of a powdercoating oven. The temperature of neither method will affect the structural integrity of the subframe or trailing arms since they're steel and not sensitive to even worst case scenario powdercoating temperatures. The possibility of hydrogen embrittlement exists though and you would have to talk to your plater about that. Baking a part after plating is a common process to deal with this issue. Zinc plating is not fast, nor is it cheap, especially when you need have something as large as a trailing arm let alone a subframe plated. The chemicals and equipment involved are expensive, and the regulatory hurdles inherent to dealing with toxic chemicals on a commercial scale add to that expense. Prep work is extensive and will be time consuming either way. Yes, places exist that will plate those large parts and large parts are routinely plated on an industrial scale, it isn't even uncommon. The question is does a place that will do it exist near you? I'd go with powdercoating, over plating on cost alone for these large parts, though the powdercoating will likely have to be removed (or not applied) on the inside of the bushing interfaces. With an unlimited budget I'd gladly plate my suspension components, though I'd do research before doing so because I am only familiar with types of plating and plating processes on a surface level. Maybe I'd do chrome like the high end lowrider guys do . As a matter of fact, if you don't already have a place in mind that's who you should ask about having it done. Find a really nice lowrider at a car show and ask the owner or contact a shop that does nice lowriders/show cars and ask about getting suspension parts plated. This reminds me that when I restore my car I will need to find somewhat local plating shop so I can have all of the hardware I remove re-plated, or at least research DIY plating.

[bradmer]

Zinc plating is like going halfway across the river, hot dipped galvanized would be better for salt corrosion. Los Angeles has 20 long foot tanks that I have sent unistrut off to, roughly $56 per 1.5" x 1.5" x 20' long. Don't know how wide those tanks are but the 4' long ones in San Diego are 30'' wide for reference. They will do all prep to get their product to stick to your material, at least wipe your stuff down good so they don't turn black when they touch it. Expect extra fees due to the Feds/State.
I do not believe there is any weakening of the metal in the process as this material was specified by the structural engineer and used to bolt panels up the exterior (vertical facade) and roof of an 18 story building downtown.
Weigh before and after if you do it.

[nando]

Galvanizing of course is best, but can cause warping on large welded parts due to the temperatures in the dip tank. Not exactly you want on suspension parts :p

[jwest11]

Why would you zinc plate a subframe and control arms. Like Varg said i dont think it will be cheap to do parts that big. They both will be perfectly fine with powder coating and if thats too expensive then just paint them. The powder coating is going to have no ill effect on these parts and is done all the time. Powder coating will help with corrosion but if you live in an area where salt corrosion is bad then I would recommend giving the car a good underside cleaning once or twice a year to help prevention corrosion from becoming a problem.

I found out the prices of powder coating and I was curious if plating would be cheaper. I don't have any experience with getting either done so i'm just weighing my options right now. I thought the heat was greater with plating, not worried about the powder coating changing characteristics. I would love to get the underside cleaned, I'll have to look around to see if there is an place in Portland that does it.

[jwest11]

The real question would be, if you could afford to zinc plate such large pieces (I'm not sure it's even possible, depends on the size of available dip tanks), why would you drive your E30 in the salt where it might matter? I'd just drive a different car I don't care about (and I do).

There's a reason plating is only used on small parts and fasteners, while paint or other less expensive coatings are used elsewhere.

There is many industrial platers near where I live that have massive tanks. I drive it in the winter occasionally, we don't get that much salt on the roads around Portland.

[jwest11]

The plating bath temperature will be higher than ambient but nowhere near the temperature of a powdercoating oven. The temperature of neither method will affect the structural integrity of the subframe or trailing arms since they're steel and not sensitive to even worst case scenario powdercoating temperatures. The possibility of hydrogen embrittlement exists though and you would have to talk to your plater about that. Baking a part after plating is a common process to deal with this issue. Zinc plating is not fast, nor is it cheap, especially when you need have something as large as a trailing arm let alone a subframe plated. The chemicals and equipment involved are expensive, and the regulatory hurdles inherent to dealing with toxic chemicals on a commercial scale add to that expense. Prep work is extensive and will be time consuming either way. Yes, places exist that will plate those large parts and large parts are routinely plated on an industrial scale, it isn't even uncommon. The question is does a place that will do it exist near you? I'd go with powdercoating, over plating on cost alone for these large parts, though the powdercoating will likely have to be removed (or not applied) on the inside of the bushing interfaces. With an unlimited budget I'd gladly plate my suspension components, though I'd do research before doing so because I am only familiar with types of plating and plating processes on a surface level. Maybe I'd do chrome like the high end lowrider guys do . As a matter of fact, if you don't already have a place in mind that's who you should ask about having it done. Find a really nice lowrider at a car show and ask the owner or contact a shop that does nice lowriders/show cars and ask about getting suspension parts plated. This reminds me that when I restore my car I will need to find somewhat local plating shop so I can have all of the hardware I remove re-plated, or at least research DIY plating.

Thanks for clearing up my temperature question! I am going to talk to many platers to see what they suggest as well. I live near Portland so I have many options that have large tanks. I wasn't sure how much of a difference in cost plating would be than powdercoating. I didn't really think about the cost of all the chemicals/regulations. If I did go with plating for the suspension components I would want to go black zinc probably. I'm definitely going to do my research before going with any option.

[jwest11]

Zinc plating is like going halfway across the river, hot dipped galvanized would be better for salt corrosion. Los Angeles has 20 long foot tanks that I have sent unistrut off to, roughly $56 per 1.5" x 1.5" x 20' long. Don't know how wide those tanks are but the 4' long ones in San Diego are 30'' wide for reference. They will do all prep to get their product to stick to your material, at least wipe your stuff down good so they don't turn black when they touch it. Expect extra fees due to the Feds/State.
I do not believe there is any weakening of the metal in the process as this material was specified by the structural engineer and used to bolt panels up the exterior (vertical facade) and roof of an 18 story building downtown.
Weigh before and after if you do it.

I'm not the most concerned about salt but just looking for a good amount of protection to cost ratio. I might end up painting everything depending on the cost in the end. Is there a significant difference in weight before and after?

[jwest11]

Galvanizing of course is best, but can cause warping on large welded parts due to the temperatures in the dip tank. Not exactly you want on suspension parts :p

Galvanizing would could warp parts, but not plating? Not too familiar on the differences.

[Shangsta]

Thanks for clearing up my temperature question! I am going to talk to many platers to see what they suggest as well. I live near Portland so I have many options that have large tanks. I wasn't sure how much of a difference in cost plating would be than powdercoating. I didn't really think about the cost of all the chemicals/regulations. If I did go with plating for the suspension components I would want to go black zinc probably. I'm definitely going to do my research before going with any option.

The only issue I can see with plating is that I dont know how they would protect the bearing housing surfaces from being plated. This is why i dont see this as a viable method for the control arms. If powder coating is too expensive just strip them down and do a good prep and just paint them, Portland is pretty mild and you wouldnt really have any crazy kind of corrosion problems.

[jwest11]

Also, when looking at my subframe tonight I noticed the two holes that are located on the inside of the subframe where the diff mounts. I'm not sure how sandblasting before powder coating would take off all the grime inside, pretty sure hot tanking them would take care of that right?