Prepping front bumbper cover for paint?
04-03-2004, 05:24 PM
#16
Rennlist Member
3M makes an epoxy like product that is mixed together and when cured
(about 2 hours) can be sanded. It remains flexible so you have no cracking worries. Good stuff, but I don't have the product numbers with me. I get them when I get home and get back with you.
(about 2 hours) can be sanded. It remains flexible so you have no cracking worries. Good stuff, but I don't have the product numbers with me. I get them when I get home and get back with you.
04-05-2004, 03:07 AM
#17
Rennlist Member
Don't use any B.S. idea like superglue. Cyanoacrylics are made for LOW olefin plastics and will fail quickly. Don't let anyone who recommends
superglue touch your project! Polyurethane molds have a LOT of release agents in it to break the mold. After the injection process takes place, the hot liquid urethane cools and must suck in mold release agents similar or in fact actually Teflon or PTFE products. Not much likes to stick to these.
So if you really want to do the job right go to the best body shop supply store that you know. Try a distributor for Glasurit as they really do tend to know their product very well. The reason for this is it is a KISS process with top notch products. This is what we do for a top notch repair. There are other products, but I know this works for decades.
Firstly, clean the part with some mild soap such as Maguires car wash soap and warm softened water several times.\
Second:Think its clean, do it again, and both sides so a big clot of dirt doesn't fall into the paint when you are spraying it for filling it.
Third: Strip the bumper very carefully with SEM or 3-M Urethane bumper stripper. Make certain to follow the directions carefully and don't let it sit too long especially in the sun or it can ruin the bumper. You can also manually strip the bumper with a d.a. sander or orbital unit, but be very careful not to sand flat spots into it. If you live in a large metro area you can also take the cover to a bumper shop who will put it in a vat and "render" the paint off of it. This is the nicest way if they take the time to do it right.
Fourth: After the paint is off and any old coats or fillers have been removed, time to clean it again. Use a little gentle soap and warm water do get rid of sanding grit and dust. Wash both sides. Then wash the cover a couple of times with TSP (trisodium phosphate) and warm water. This works very nicely to remove olefins and other waxy procucts essectial to plastic manufacturing. Just when you think you can't get it any cleaner, wash it again and give it a final wash with distilled or filtered water. Make sure it isn't outside to dry in the sun and don't let it leave any mineral residue when drying.
Finally your cover is clean and ready for work.
Fifth, identify any areas that had fillers in them or need to be repaired by anything more than filler primer. That would be any areas over 0.030 inches deep at the most.
Sixth,
superglue touch your project! Polyurethane molds have a LOT of release agents in it to break the mold. After the injection process takes place, the hot liquid urethane cools and must suck in mold release agents similar or in fact actually Teflon or PTFE products. Not much likes to stick to these.
So if you really want to do the job right go to the best body shop supply store that you know. Try a distributor for Glasurit as they really do tend to know their product very well. The reason for this is it is a KISS process with top notch products. This is what we do for a top notch repair. There are other products, but I know this works for decades.
Firstly, clean the part with some mild soap such as Maguires car wash soap and warm softened water several times.\
Second:Think its clean, do it again, and both sides so a big clot of dirt doesn't fall into the paint when you are spraying it for filling it.
Third: Strip the bumper very carefully with SEM or 3-M Urethane bumper stripper. Make certain to follow the directions carefully and don't let it sit too long especially in the sun or it can ruin the bumper. You can also manually strip the bumper with a d.a. sander or orbital unit, but be very careful not to sand flat spots into it. If you live in a large metro area you can also take the cover to a bumper shop who will put it in a vat and "render" the paint off of it. This is the nicest way if they take the time to do it right.
Fourth: After the paint is off and any old coats or fillers have been removed, time to clean it again. Use a little gentle soap and warm water do get rid of sanding grit and dust. Wash both sides. Then wash the cover a couple of times with TSP (trisodium phosphate) and warm water. This works very nicely to remove olefins and other waxy procucts essectial to plastic manufacturing. Just when you think you can't get it any cleaner, wash it again and give it a final wash with distilled or filtered water. Make sure it isn't outside to dry in the sun and don't let it leave any mineral residue when drying.
Finally your cover is clean and ready for work.
Fifth, identify any areas that had fillers in them or need to be repaired by anything more than filler primer. That would be any areas over 0.030 inches deep at the most.
Sixth,
04-05-2004, 03:34 AM
#18
Rennlist Member
As I was saying before my poor typing skills got the better of me--
Sixty, choose a method to fix the problem areas. On torn bumper I recommend plastic welding. You can identify most good manufacture's materials by a three digit code on them. Take that code to the body supply store and see what they can tell you. You can normally rent a welder for $10 a day and buy $5 woth of sticks to fix a pretty long tear. Groove out the crack from one side and weld it. Groove it out from the other side and weld it as well. Leave the weld a little proud if possible. Grind off excess and fill low spots with a fine plastic body filler appropriate for that specific plastic. If it is a urethane plastic, use a urethane or poly urethane two part filler. This can also be used on the small scrapes.
If you can't get a plastic welder ask for a Dominion Bumper Repair Kit. It has a two part urethane adhesive that is wickedly sticky and flexible. You first prep the back side with a grinder to scuff it and improve adhesion by increasing the texture and surface area. Make sure the area is clean and grooved on both sides. At the end of the tear, drill al 3/16 inch hole to serve as a crack stop to ward off crack propogation On the back side use the adhesive with some special kevlar or fiberglass cloth which gives it tremendous strength. be liber with the spreading keeping it about 0.050 inches thick and about 1.5 inches wide with the crack in the center. over lap the crack at the end by about an inch. One the back is done but not fully cured, do the front and try to keep it a little proud as well. You can always sand it off later.
Seven: Now that all the filler have cured, sand them down gently smooth to the cover and clean the cover with some clean air. The plastic should now be washed with aqueous based plastic cleaner.
Eight: Once it is clean this is done a plastic adhesion and flew promoter can be sprayed over the bumper. This will allow primer to best stick to the cover and lessen the likelihood of it coming off.
Nine: Make sure all the big areas are still filler and it is ready to prime with a high build urethane or polyester primer. I like fine grind urethane building primers by RM for the money. They seem really watery, but their fine grind really covers quickly.
Ten: The cover is primed a couple of times and all scratches are gone. Sand it smoothly with a d.a. to around 400 grit some people like 600. I think it is a little fine and harms adhesion promotion. After it is sanded smooth, blow all the dust off the cover and use a gentle brush and brush the whole cover to get the dust out of the microscopic cracks. Blow it off again and amazingly more dust comes off.
Eleven: Clean the cover again with a aqueous based cleaner to float all the dust up out of the cracks. Do it twice and blow dry.
Twelve: Tack rag it and get ready and clean to pain
Thirteen: The luck number! Hopefully you prepped well because here is where it really pays off. Choose your paint and make sure that you ad flex additive to it if they recommend it. You can use single or base clean coat.
Fourteen: Don't use lacquer, please!
Fifteen: Have a good painter paint it
Sixteen: If you were in a clean paint booth, you might not even have to sand or buff it! Likely you will have to color sand it with 2000 and 3000 grit and then polish it.
Seventeen: Let it sit over night and carefully intall it in the moring putting lite pull masking tape over corners that can be damaged. Have two people install the cover so one can tighten will the other watches and guides his buddy on fitament.
Eighteen: Swear you will never do body work again and go grab a few beers!!!!!
Anyway, there are some things left out like sanding finish and grit selection as it really requires a trained eye to do it correctly. Talk to a reputable supplier as all paints are good. I just like Glasurit and RM because they use the finest products and I believe give the nicest results.
Good luck and read the bottom disclaimer:
Before starting, check with you local supplier about the types of cleaners, strippers and paper grits that you will need to use in order to be warrantied if their product fails. They all differ. Painting can be harzardeous to your health, blah, blah, blah. It can cause three headed children and increased irritability from solvent exposure. Always wear safety glasses and respirators when sanding and painting.
Hope you found this thread helpful,
Motorsport
Sixty, choose a method to fix the problem areas. On torn bumper I recommend plastic welding. You can identify most good manufacture's materials by a three digit code on them. Take that code to the body supply store and see what they can tell you. You can normally rent a welder for $10 a day and buy $5 woth of sticks to fix a pretty long tear. Groove out the crack from one side and weld it. Groove it out from the other side and weld it as well. Leave the weld a little proud if possible. Grind off excess and fill low spots with a fine plastic body filler appropriate for that specific plastic. If it is a urethane plastic, use a urethane or poly urethane two part filler. This can also be used on the small scrapes.
If you can't get a plastic welder ask for a Dominion Bumper Repair Kit. It has a two part urethane adhesive that is wickedly sticky and flexible. You first prep the back side with a grinder to scuff it and improve adhesion by increasing the texture and surface area. Make sure the area is clean and grooved on both sides. At the end of the tear, drill al 3/16 inch hole to serve as a crack stop to ward off crack propogation On the back side use the adhesive with some special kevlar or fiberglass cloth which gives it tremendous strength. be liber with the spreading keeping it about 0.050 inches thick and about 1.5 inches wide with the crack in the center. over lap the crack at the end by about an inch. One the back is done but not fully cured, do the front and try to keep it a little proud as well. You can always sand it off later.
Seven: Now that all the filler have cured, sand them down gently smooth to the cover and clean the cover with some clean air. The plastic should now be washed with aqueous based plastic cleaner.
Eight: Once it is clean this is done a plastic adhesion and flew promoter can be sprayed over the bumper. This will allow primer to best stick to the cover and lessen the likelihood of it coming off.
Nine: Make sure all the big areas are still filler and it is ready to prime with a high build urethane or polyester primer. I like fine grind urethane building primers by RM for the money. They seem really watery, but their fine grind really covers quickly.
Ten: The cover is primed a couple of times and all scratches are gone. Sand it smoothly with a d.a. to around 400 grit some people like 600. I think it is a little fine and harms adhesion promotion. After it is sanded smooth, blow all the dust off the cover and use a gentle brush and brush the whole cover to get the dust out of the microscopic cracks. Blow it off again and amazingly more dust comes off.
Eleven: Clean the cover again with a aqueous based cleaner to float all the dust up out of the cracks. Do it twice and blow dry.
Twelve: Tack rag it and get ready and clean to pain
Thirteen: The luck number! Hopefully you prepped well because here is where it really pays off. Choose your paint and make sure that you ad flex additive to it if they recommend it. You can use single or base clean coat.
Fourteen: Don't use lacquer, please!
Fifteen: Have a good painter paint it
Sixteen: If you were in a clean paint booth, you might not even have to sand or buff it! Likely you will have to color sand it with 2000 and 3000 grit and then polish it.
Seventeen: Let it sit over night and carefully intall it in the moring putting lite pull masking tape over corners that can be damaged. Have two people install the cover so one can tighten will the other watches and guides his buddy on fitament.
Eighteen: Swear you will never do body work again and go grab a few beers!!!!!
Anyway, there are some things left out like sanding finish and grit selection as it really requires a trained eye to do it correctly. Talk to a reputable supplier as all paints are good. I just like Glasurit and RM because they use the finest products and I believe give the nicest results.
Good luck and read the bottom disclaimer:
Before starting, check with you local supplier about the types of cleaners, strippers and paper grits that you will need to use in order to be warrantied if their product fails. They all differ. Painting can be harzardeous to your health, blah, blah, blah. It can cause three headed children and increased irritability from solvent exposure. Always wear safety glasses and respirators when sanding and painting.
Hope you found this thread helpful,
Motorsport
