When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I know this topic is redundant but I can not find search for paint vs powder coating S4 valve cover and intake topics. Read previous discussion but don't remember the difference except sand could get into the flappy in the intake. Posting links to this thread is appreciated.
Taking advantage of down time to redo my S4 valve covers and looking for pros/cons of paint vs powder as I know issues with magnesium like in BMW. Thanks.
I recently powder coated the valve covers on my '87 and '88 and they came out great, so cannot speak to paint (I'll let other chime in on the merits vs any downsides of paint).
Peter, sorry I missed your call- up to my butt in hospital prepping. My vote is for powdercoating, give OC plating a call and ask for Dan, (714) 532-4610.
I've stayed away from this thread, but with the mention of this --^ I figured it was time to voice my opinion. Shaun from Tru6 (see https://rennlist.com/forums/928-foru...l#post16344013) in that thread has been doing my intakes, cam covers, etc., for several years now. Most of those 928 parts in that thread are from my clients' 928s. I'm pretty 'sold' on Cerakote and Shaun's work as a much better alternative than powder coating for the intake and cam covers. Your mileage might vary and that's fine. Do note that quality isn't cheap.
@Bmw635 If you are a DIY kinda guy @chart928s4, when we pulled his engine, did his own Cerakote (and picked his own colors) rather than go with Shaun at Tru6 mainly for schedule and just-wanted-to-do-it-himself reasons. His coating is holding up great after quite a few miles.
Thanks for the vote. Looks like chromate coating the magnesium is the key before any finishing is applied and a thin finish coat to allow magnesium to gas out also help. Plan to redo my BMW M62 valve cover the same as the 928 as the powder coat is bubbling up after 10 yrs with only 4k miles.
Yes, I am hands on everything so plan to DIY. Thanks.
PM me if you want the full story. Short version is: Beat the crap out of the old coating with anything that will work (wire wheels), bake the parts at 200 for 4 hours, wash (especially inside the intake) with a dryer brushand change the water 6 times using Zep Citrus Degreaser, rinse thoroughly, spray on white vinegar, rinse again, dry, brush liberally with Sanchem 3400 and air dry, spray with Cerakote Glacier (ambient air cured) within a few hours.
Brian @olmann 's thread was the inspiration. The man is a legend among intake DIYers. The air cure Cerakote is fantastic in every way and is the only thing I can do to improve on his excellent thread.
I experimented with a non-conforming DYI approach using the POR15 series of products. Started with the POR15 degreaser, then used a combination of scraping and paint stripper (Multi-Strip Advanced). Degreased again and applied the POR15 Metal Prep. I coated the inside of the intake with 3 coats of POR15 Gloss Black Rust Preventative paint - a tiny paint roller on the end of a bottle brush enabled me to get into each intake runner completely. I did a single coat of POR15 Gloss Black on the outside, and actually wiped most off on the top surface with the cast lettering, gasket surfaces and inside the fuel injector bores. I scuffed up the outside with sandpaper and primed with 2 coats POR15 Metal Etching Primer and top coated (2) with Rustoleum High Temp Aluminum color. Came out great - how long it lasts only time will tell - I'll report back, it's only been a few weeks.
Anyone familiar with the POR15 Gloss Black knows it sticks to everything, and forms a water tight, plastic-like coating that will not crack, chip or peel. I used it on some rusted, NLA water lines on my '99 Audi, and knew I had to try it on the intake.
Coated with POR15 Gloss Black Final finish - POR15 Gloss Black inside Final Result - Now proud to open the hood - I know the air filter is upside down - car came that way
Thanks for the vote. Looks like chromate coating the magnesium is the key before any finishing is applied and a thin finish coat to allow magnesium to gas out also help. Plan to redo my BMW M62 valve cover the same as the 928 as the powder coat is bubbling up after 10 yrs with only 4k miles.
Yes, I am hands on everything so plan to DIY. Thanks.
Interesting. Can you explain what that chromate coating is? Or, do you have a link?
I'd like to second Red Flash's question, as I am confused about this aspect of refinishing as well. I contacted Cerkote about this, and gave them the alloy name, to ask about precisely these kinds of questions. Their response was not really detailed, like, at all, but the indication was that there was nothing particularly special about the prep for Mg alloys. I really like the idea of Cerakote, as it's something that I think I could do myself but I'd really hate it if things fail due to improper prep work.
Cerakote wasn't helpful for me either. But I can weigh in with what I found when I did some research. Caveat: Not a metallurgist or chemist - all knowledge from Internet reading and vendor information.
Magnesium, aluminum, and titanium for whatever reason do not have a surface that allows most regular paints to adhere. Etching primers are one way to solve the problem, and they essentially add adhesion area by roughening the surface. But the bond is still paint/metal.
A "chromate" coating has been used since the early 20th century to ensure adhesion for many conventional paints. It is a requirement for certain aerospace military requirements where etching primers are not allowed. The purpose of these is to provide a surface that will both stick to the metal on one side and be paint friendly on the other. They do not roughen the surface but merely adhere. The best known is Alodine 3700, a brand name now owned by our Loctite friends at Henkel. Alodine has several formulations of which 3700 is the one for magnesium. The chemicals are fairly toxic and are controlled by many regulations. However, contrary to some assertions they are available in every state for industrial use. Alodine is available in wipes, gel and liquid.
Answer to a question that wasn't asked: Sanchem 3400 is another more recent line of coatings that work the same way. However, the product is non-toxic and unregulated, and available by the gallon from the manufacturer by mail order. I (and I think Brian Olmann before me) had a nice conversation with their chemist about the intake material with some general intermolecular topics thrown in.
Both Alodine 3700, Sanchem 3400, and many other are approved by the US Air Force in publicly available documents for all aerospace applications. And if anyone from Massachusetts wants some Sanchem 3400, please let me know. I have at least 3/4 of the gallon left.
Cerakote wasn't helpful for me either. But I can weigh in with what I found when I did some research. Caveat: Not a metallurgist or chemist - all knowledge from Internet reading and vendor information.
Magnesium, aluminum, and titanium for whatever reason do not have a surface that allows most regular paints to adhere. Etching primers are one way to solve the problem, and they essentially add adhesion area by roughening the surface. But the bond is still paint/metal.
A "chromate" coating has been used since the early 20th century to ensure adhesion for many conventional paints. It is a requirement for certain aerospace military requirements where etching primers are not allowed. The purpose of these is to provide a surface that will both stick to the metal on one side and be paint friendly on the other. They do not roughen the surface but merely adhere. The best known is Alodine 3700, a brand name now owned by our Loctite friends at Henkel. Alodine has several formulations of which 3700 is the one for magnesium. The chemicals are fairly toxic and are controlled by many regulations. However, contrary to some assertions they are available in every state for industrial use. Alodine is available in wipes, gel and liquid.
Answer to a question that wasn't asked: Sanchem 3400 is another more recent line of coatings that work the same way. However, the product is non-toxic and unregulated, and available by the gallon from the manufacturer by mail order. I (and I think Brian Olmann before me) had a nice conversation with their chemist about the intake material with some general intermolecular topics thrown in.
Both Alodine 3700, Sanchem 3400, and many other are approved by the US Air Force in publicly available documents for all aerospace applications. And if anyone from Massachusetts wants some Sanchem 3400, please let me know. I have at least 3/4 of the gallon left.
End brain dump.....
Ah, Alodine 3700. I think that might still be available in the US, yes. But, in the EU, I think it was struck by the REACH requirements. I didn't know that would be for Magnesium. Thanks for the commentary. Very interesting.
03-23-2020, 02:01 AM
Valve cover refresh.
