weld thru primers

admin

Hi- I know this topic has been probably beaten to death,but being new to the website and still a rookie at welding--I have to ask a couple of questions: First---What ''Weld thru Primer"" do you guys/gals get the best results with---U-POL/ SEM/ 3M/ Duplicolour etc...Second: Do they really work-or am I just wasting my time.   3M /  duplicolour  & SEM    are here at my local autoparts store, but i keep getting different opinions  on how they work or don t work. Thanks in advance JIM
Reply:Hey Jim. They do work if used properly. When you have the panels ready to weld put a good coat on the area surrounding the weld spot that you won't have access to like a lap joint and let it dry good. I usually use SEM cause it is easy to get along with 3m where I get my paint. When you weld it will melt and burn some off but for most part it will melt back into place and that is where you get your protection from. I think it is unwise to rely only on this though. Get yourself some "rust fighter" of some sort which is a waxy non drying spray to coat inner panels with. This stuff seals against moisture and works great. They will sell a wand to go with it that will put out a 360 degree pattern to get all areas. Usually just drill a hole in a panel and stick wand in then spray as you are pulling the wand out. If you want then put a small plug back in hole.Millermatic 252Lincoln 175 plusTA 185tswTA 161stlhypertherm pmax 45Victor torchHenrob torchAn S10 for each day of the week
Reply:Thanks -S  Obsessed-- Excellent answer--Yes I can get SEM/3M here at my local Advance auto / Autozone & Carquest---Now I have another question--In your opinion ----'' What would be the coldest/ minimum  temperature or month  you would attempt to weld a car floor panel outside.I live in Mass.  and winter is coming up fast.  Thanks JIM
Reply:Originally Posted by JIM OWENSWhat would be the coldest/ minimum  temperature or month  you would attempt to weld a car floor panel outside.I live in Mass.  and winter is coming up fast.  Thanks JIM
Reply:just from basic  priming/painting --I would think  50 o  would be the absolute lowest I could go. Makes sense right
Reply:I've used them all in my body shopI'd say the best is between u-pol & 3m with 3m probably being my preferred choice. next best would be SEM & last on this list would be duplicolor which is kinda crap compared to the rest.ideally I would want to see at least 60 degrees F for the curing cycle of any of these sprayed materials. most un-activated single component liquid products like this do not cure properly under 60*Fmiller 330a bp TIGmiller dynasty 200DX TIGmillermatic 185 MIGthermal dynamics cutmaster 101 plasma cuttersnap-on YA5550 plasma cutterhypertherm powermax 30 plasma cutterbaileigh CS225 cold sawetc....
Reply:Well Jim I wouldn't worry about temperature. With thicker steel, the surrounding area tends to act as a heat sink and suck the heat away from the weld real fast till it warms up and this is what can cause cracking in weld area. With the thin stuff it pretty much all warms up instantly in the area near the weld so it doesn't pull the heat away. However it definately wouldn't hurt to take a heat gun and warm the area up to 80-100 degrees F just to make sure there is no moisture in the form of ice or frost. Although that would pretty much get driven off right away there could still be some porosity. Now if you are using the weld through primer on the area to be welded then I would make sure that there is a heater warming the parts up to at least 60 degrees before spraying them and then probably 80-100 to dry it. The solvents in the primer need to evaporate or they will give you issues welding. So if you can stand it, you could weld as cold as possible. What are you working on?Millermatic 252Lincoln 175 plusTA 185tswTA 161stlhypertherm pmax 45Victor torchHenrob torchAn S10 for each day of the week