Phosphating and Chromating

[non-stick]

I don't know if you all keyed into the fact that there are different types of "wash" treatments as far as bond goes on this site, but I'll give you the inside skinny before Caswell cross-lists these puppies.

We all know that a phosphating solution to your steel available in the powder coating section. But what do you do for that home-run grip on aluminum or copper/brass?

For aluminum, ALCHROM880 is a great choice to use. Same pretreatment, but best suited for non-ferrous white metal such as aluminum. It's even mil-spec approved! ( approved by the U.S. Government as a viable treatment). For those of you coating valve-covers and intakes.... THIS is your home run in the prep-process.

For other metals you might be coating in the brass/copper family, A02 is the way to go. In my humble opinion, brass and copper (especially) are the hardest substrates to powder coat and this would best help your adhesion during the whole process. Order this product and you'll no doubt have a good chance at longevity for your coating.

Stainless has always been a bear to coat as well. SSB370 is the way to go if you need it. Who knows... you may have a reason to finally powder coat that DeLorean that's sitting in your garage after all!

Tip for those who coat Stainless Steel and copper/brass while on the subject. When these metals heat, they oxidize very quickly. If anybody's ever tried to buff that off, you'd know what a pain in the you-know-what that could be. Make a simple solution of Hydrochloric Acid (found at your local hardware store) and water and "dip" the part for approx 30 seconds. Right before your eyes, the oxidation will sluff off and leave you with your original finish yet once again. It's even a good idea to do this on your cookwear once in a while to keep those old pots and pans looking "fresh" for years to come . Please remember to wear the appropriate eye/hand protection while doing this. HcL is VERY acidic and will burn most anything it comes in contact with almost immediately. Hope that helps somebody out there if they had an adhesion problem......Russ

[mcaswell]

These products are available at http://www.caswellplating.com/aids/metal.htm

[drfjr1976]

I am going to purchase a gallon (which will make 32 gallons) of the Iron Phosphate Primer. The thing I was needing to know is, Will the ceramic boiling heaters http://www.caswellplating.com/suppli...c_heaters.html work for this solution since it will be a 30 gallon tank?
or will the ceramic plating heaters be better? http://www.caswellplating.com/supplies/heaters.html
I know the boiling heater is made to bring the solution temp to a boil which is defanetly to hot for the phosphate and that the plating heater is preset at 110 degrees. Phosphate range 70-160degrees. But I didn't know if I would need the larger one since it is 30 gallons. Thanks

[drfjr1976]

OK got a nother "?" for you. How does the Phosphate leave the finish? Does it change the apperance in any way, color or texture? The reason I am asking is because i do a lot for aluminum parts that I polish certain areas of and I do this before coating.
If the phosphate will affect the polished areas, will the High temp tape keep the phosphate off. Or will it remove the tape since it is a detergent so to speak.
And if the tape will protect the areas, will it need to be removed and fresh tape applied before coating.

Thanks again

[non-stick]

ok... first things first.....

The second heater ( PRODHEAT110 )is the more logical choice as they "regulate" the water to 110F. Of course... for 32 gallons, this may be taxing for just one element. I'd say that one will be good per 10 gallons otherwise you may not get that temperature up from a cold start. It may even be as low as 5 gallons per heater, I don't know the specs on this one to be quite honest with you. I would assume just for giggles on this one... that if you were going to be doing this on a constant basis, 3 heaters from a dead stop at room temperature would heat up a tank of the solution nicely.

With that said...... traditionally in an industrial situation, the iron phosphate is set up into a large washtank in stages. Temperature is "targeted" to be approximately 140F but there's always a loss of heat value when factoring in the ambient air temperatire, heat loss due to surrounding part and tank wall temperature, etc. The temp usually settles down to 120F.... so you won't be that far off base in your "tank" configuration. Usually the higher temperatures dissolve oils faster and create a quicker chemical reaction from phosphate to substrate which is why you have that "higher end curve" going. I personally see no difference between 160F for 30 seconds and 110F for 7 minutes. (much like the cure schedule on a powder if you pay attention!).

Next we have your question about how a phosphate leaves a finish. Well... chemically speaking, the "salts" or phosphates from your solution are attacking your substrate on a microscopic level. Oils are washed away and the pores of the metal are exposed. Therefore, leaving room for the structure of the phosphate to reside in. This is what is known as chemical oxidation. (use this example if it helps you.... put a piece of copper out on the ground. Nice and shiny, right? After years of rain, the water and natural "salts" or "minerals" in the air turn the copper green through oxidation. Phosphating is no different. Your metal is steel, your vehicle is the water, and your "salts and or minerals" are the phosphate. Same process, just that the time has been sped up due to heat and concentration of chemical reaction in a shorter time frame. Period). Anyways... when your part leaves it's phosphate wash, it is then rinsed to stop and neutralize the chemical reaction from happening. You do this simply by rinsing it with clean water. Then the part is dried. Either via an air-gun, or heating in a warm oven. NEVER wipe the water off or for that fact.... touch the phosphated steel with your bare hands. The reason is this : you have just applied a crystaline structure and washed the metal of any oils. When you touch it, the structure has been knocked down and the oils from your skin are left on the metal. Basically, you just reversed the process of which you just applied. Hang it from a hook and dry it properly. What you will be left with basically is a piece of steel that through the magic of phospating, looks for the most part blue. It's not unusual to see red,yellow,green,orange,etc.... but traditionally.... the colour left behind is a sort of bluish steel. All that happened here was the light bouncing off and refracting off of the surface of that crystaline structure. Different chemicals (or salts) will refract light differently. So don't be surprised when you see your part look sort of tye-dyed,lol. It's supposed to look that way. A pleasant (albeit brief) thing that just happend is this in a nutshell.... salts are minerals. Logic dictates that minerals turn to metals under the right conditions. So basically... you just degreased the part, filled the voids with chemically treated "metals" and not only primered the part, but "smoothed out" the conductive surface from applying a like minded "metal" evenly across the surface. Period. Of course... this leads us to your next question....

Does phosphate change the appearance of the metal in any way. Well... just to go over what I said. Basically, yes. You've "oxidized" your part chemically speaking. For steel, iron phosphate makes a "blue" because it is a ferrous (metallic) metal. Zinc Chromate (PRODALCHROME880) for aluminum will "yellow" in appearance. Can it be taken off after you've coated? sure it can! It's like any other oxidation. Just reverse the process. Wipe down with something acidic or base to release the bond from the structure and buff it to a shine. If you have areas where you have raised lettering on a valve cover, let's say? coat the entire thing and just take a flat sander and sand until you hit metal. Finish off with a high grit paper to get shine if you wish. You may be able to mask the part AFTER you phosphate or chromate, as the "detergent" will basically get underneath your masking and release the glue from the tape. Just be careful handling an already phosphated piece if you are going to do that,k?

I think I basically answer your questions,no? Just keep in mind... iron phosphate for steel,zinc chromate for aluminum. That's the general rule. Hope that helped and didn't make you more confused,lol.... Russ

[drfjr1976]

HAHA I was able to keep up with you on all that and I know that you have mentioned before about useing Zinc Chromate (PRODALCHROME880) for aluminum, but I was under the impresion, from the web page, that the phosphate could be used on steel,zinc and aluminum. I know that Zinc Chromate is better for aluminum but I was trying to keep my chemical colection to a minumum. One chemical for cleaning.

[non-stick]

hey! Either I'm becoming a better communicator or you my friend, are learning a few new things and becoming a more informed coater! ( I vote for the latter.... I know for a fact my communication skills havn't changed,lol). Yes, while the phosphate can indeed be used on aluminum... it's a situation of good/better/best. I won't usually recommend something if there's a better alternative out there or if you have no choice. Here on the site you do have a better alternative and a choice in your options and therefore, I suggested it. After all...... we both know that you only want to powder coat something the 1 time, am I right? In that 1 time deal... you do indeed want the best for your parts and possibly a clients' word of mouth advertising because "this stuff is awesome and I have no complaints", am I right? Small investment for good advertisement, let's say. I suggest phosphate for steel and chromate for aluminum, and that's all I'm gonna say on that one. Your decisions are your own and my knowledge is based upon the mistakes I've made in the past. One may take the risk themselves and learn like I did and gain wisdom from another's errors. That's all I'm saying ..... Russ

[drfjr1976]

I got ya.
Thanks

[drfjr1976]

Originally Posted by non-stick

Anyways... when your part leaves it's phosphate wash, it is then rinsed to stop and neutralize the chemical reaction from happening. You do this simply by rinsing it with clean water.

Clean tap water or should we be using distilled?

I know.

[non-stick]

clean tap, my friend. Unless you're doing something way out in left field like medical instruments or such that need to have exotic powders and plasma treatments.... it's just not necessary. Rinse with clean tap water, dry off and you'll be good to go ..... Russ