TSP--Flash Rust

Wed Jun 06, 2007 9:09 pm

When using the "real" stuff (TSP) most folks have reported little or
no flash rust. I too, am using TSP and when I remove an item from the
tank, I can actually watch it rust :shock: So after considerable
cogitation, I was wondering if the WATER might have something to
do with the flash rust. My water is provided by the city and is highly
chlorinated. I was wondering what your water sources might be, and
if that might be the reason for my flash rust. If so, I will seek a
different water source for my next tankful.


Wed Jun 06, 2007 9:45 pm

I hate to disagree with folks, but bare metal will rust quickly.... I don't care if it's TSP or washing soda in the tank. I have flushed the parts with water, dried them, cleaned em with alcohol and primed them as soon as I can. If I don't the part will invariably start to rust. I do live close to salt water, but suspect it would be the same anywhere, just take a little bit longer.

Some parts are near impossible to get all the rust (battery boxes are a good example) so I will use a brush on primer (Rustoleum is about all that is commonly available) to seal the part better.

I also never let a sandblasted part go overnight without priming it. I always prime those with a brush too.

Could be I am too particular??

Wed Jun 06, 2007 10:15 pm

You can wipe on a thin coat of Kroil or mineral spirits to stop the flash rust. When you get ready to paint, wash the part or surface with a strong solution of Dawn or Simple Green. It should not flash rust as fast. :wink:

Wed Jun 06, 2007 10:17 pm


None of the parts that I take out of my tank flash rust. Cecil also has the same results as well as others..

However, if the TSP is used at less than 2kg per 55US Gallons, I am not sure what will happen. I also believe the it isn't necessarily the TSP as the TSP Free product works the very same way, so I think it is one of the secondary ingredients or maybe the fillers???? that help prevent flash rust.

TSP and TSP Free are the only products that have demonstrated this peculiar result..

Not sure what else to say, except that I have parts including 4 front rims that have NO flash rust after 3 years of sitting after the trip in the tank... :roll: :shock: :? :!: 8) 8) :D

Wed Jun 06, 2007 10:29 pm

I wonder though, like in your case Rudi, if the TSP leaves a protective residue on the parts? or do you wash yours when you take them out of the tank? I must say that I hvae had very good results after the tank. No flash rust has occured for me, and i wash and wipe off the parts when they levae the tank.

Thu Jun 07, 2007 6:44 am

I think Bob might be on to something with the well water vs. city water in the tank.

Thu Jun 07, 2007 8:04 am

I would be surprised if the chlorine in your city water has a high enough concentration to cause a difference. If memory serves me most city water supplies keep a residual .12 -.25 ppm in their city water after treatment. This is quite low and I would be suprised if it would cause any measurable difference in corrosion rates.

The sodium in TSP disassociates completely when mixed with water. Lots of sodium atoms means lots of electrolyte means very strong coductor of electrons in solution.

If you are having that much trouble with rapid oxidation of your part I would suggest rapidly washing them in mild soap and water, rinse well, dry and use an etching primer.

My local sandblasting dude keeps his family fed by blasting cast parts from a local foundry simply because the foundry can't prime them fast enough to keep them from rusting.

Hope you find the solution (pardon the pun)


Thu Jun 07, 2007 9:17 am

I have a 55 gallon tank (thanks to Cecil & Rudi) and use a full 4 1/2 lb box of Savogran TSP in it. I fill the tank with our well water that goes through a two step treatment process to make it potable. It first goes through a filter media to remove particulate and raise the PH to 'neutral' from about 5.2. It then goes into an iron removal media using a NaCl solution to charge the media (versus a Potassium Chloride solution as some use) that reduces the iron from 4 parts per million to .5, otherwise we have tomato soup for water.
Recently I ran an exhaust manifold through the tank for 3 days and it came out great. It had the usual black appearance that comes from the conversion process with the TSP solution. With the warm weather that we had it dried real quick and I thought it would be fine. Came out the next morning and it was covered with rust dust. Same thing happened with a hammer head that I did last week. We've been having some pretty high humidity lately so I attribute the flash rust to that.
My $.02

Flash rust

Thu Jun 07, 2007 10:50 am

I used to work in a metallurgical lab and had to prepare specimens for analysis on a microscope. If they were steel, they had to be cleaned and dried immediately. I used a wash bottle with alcohol and then a commercial grade "hair dryer" to evaporate the alcohol and dry the part. It was easy to do with small parts. For big stuff you could use a garden sprayer to get the alcohol on fast.

You could protect these parts by sealing them in a plastic bag with a sack of silica gel (the "do not eat" stuff) to keep them high and dry until you are ready to paint. You can buy big bags of the stuff and when they are saturated you can bake them in the oven so they can be reused over and over.


Thu Jun 07, 2007 11:13 am


That's a good tip.

BTW, welcome to the forum. :D

Thu Jun 07, 2007 3:00 pm


I think I just found the Cub Tip of the Week. Thanks :!: :wink: :D

golly gee

Thu Jun 07, 2007 3:19 pm

aw shucks...
And from such august posters...
Bob the former lurker

Thu Jun 07, 2007 4:04 pm

Welcome aboard Bob. Glad to have anonther person on the site that can answer questions for me. :lol: :lol: :oops:


Thu Jun 07, 2007 9:33 pm

Great tip, Bob. I'm going to try it. Welcome aboard! Oh, and by the way, them guys ain't august posters, they's June posters. :lol: Kit

Thu Jun 07, 2007 10:16 pm

The only thing that will prevent flash rust before you can prime is to treat the surface with a phosphoric acid solution. This is pickling, and converts the surface to a non reactive phosphate. While TSP is a phosphate itself, it is the salt of a phosphate (i.e. it is already reacted) , hence will not react further with the steel the way phosphoric acid will. The iron molecules need to be chemically reacted (phosphated) to convert them from active to inactive form (non rusting). Once phosphated, the part has to stay dry. If it gets wet, the phosphate dissolves and rust can resume.

Many phosphoric acid pickling solutions are available: Picklex20 and Must For Rust (Home Depot) are commonly used. PPG and DuPont paints have solutions in their coatings lines. Etch primer contains phosphoric acid, but doesn't work as well as treating directly with acid solutions first followed by say, an epoxy primer.

Electrolysis electrochemically activates the surface so it is more reactive than normal clean steel. Moisture from the air contacts the active surface and . . . . there's flash rust. Dry climates have much less of a problem with flash rust. The salt used to make the electrolysis bath only facilitates the electrolysis process. If you use any sort of oil to protect coat the surface it will later prevent the primer from adhering properly unless you wipe it thoroughly with laquer thinner first.