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  #1  
Old 11-01-2016, 01:49 PM
Stretch Stretch is offline
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Default Phosphoric Acid Panel Wiping Advice Needed

Hi folks. I'm having a few issues with phosphoric acid on bare steel panels. I'm getting a very streaky effect (see pictures) with a kind of rusty coloured haze, rather than a nice, uniform steely-blue finish like I've had in the past. I've diluted the acid to approx 30% strength, and am wiping on with a cloth, leaving for 30 mins, then washing off with a cloth and clean water. Any helpful tips or advice, as I'm scratching my noggin at the mo... 😄



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Old 11-01-2016, 03:00 PM
Jim Tomczyk Jim Tomczyk is offline
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Hi Stretch
whenever I've used a phosphoric etch on steel I've brushed it on, left it for 30 mins until the steel looks a dull grey , then brushed on another thin coat of etch wiping it off with a clean dry cloth immediately and leaving it to air dry before priming within 24 hours to avoid a flash coat of oxidisation. Ive never had a paint reaction using this method as long as you thoroughly wipe off and dry, making sure any etch is thoroughly wiped out of corners, creases etc .
Ive never washed off with water which I can only imagine will encourage and accelerate an oxide layer - which your streaks look like to me? , the phosphoric etch I've always used has been a liquid etch rather than a gel and is a proprietary branded product.
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Old 11-01-2016, 07:46 PM
Oldnek Oldnek is offline
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It looks like flash rusting to me, I get a lot of this when I use vinegar to clean surface rust of, then wiping with clean damp rag afterwards. Steel Wool or Scotch Brite then Etch straight away, as the Ocean is only 500mtrs away to me.
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Old 11-01-2016, 09:09 PM
Mike Rouse Mike Rouse is offline
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Looks like the rag gave inconsistent application. Paint brush is the way to go. Have to coat evenly for an even result.

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Old 11-02-2016, 08:59 AM
skintkarter skintkarter is offline
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Matt, I was always told not to let the phosphoric dry out on the panel. All of the sheetmetal I've made for the Group 5 was washed with Tergophos (acid & degreaser) via a squirty bottle and scuffed with some worn out 300 grit scotchbrite. Then washed off with the hose (admittedly rainwater, cos I'm a Hillbilly) but crucially the panel dried off. I then spray on (cheapo spraygun that I don't care for) Epiphos which is an acid based clear coat. This holds up pretty well before you get to the paint stage.

20160807_130903.jpg
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Old 11-02-2016, 10:13 AM
Stretch Stretch is offline
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Thanks guys! Richard, I wonder if I can get that product in the UK? A clear coat etch... Mission on! Ta
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Old 11-03-2016, 12:54 AM
skintkarter skintkarter is offline
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Quote:
Originally Posted by Stretch View Post
Thanks guys! Richard, I wonder if I can get that product in the UK? A clear coat etch... Mission on! Ta
Matt
You are welcome Matt. Agents here are Chemetall, but think that it's an NZ only product obtained after Chemitall gobbled (Corporate term...) Tergo Industries and Epiglass which were small NZ Companies. Surely must be a UK equivalent.

http://www.chemetall.co.nz/
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Old 11-03-2016, 01:01 AM
skintkarter skintkarter is offline
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But wait, there's more... From the Chemetall NZ website

Epiphos is a chemically active primer which reacts with ferrous substrates resulting in a chemical bond far stronger than physical adhesion bonds (epigenic coating). It has water displacing properties and may be applied by brush, roller, spray or dip operation. Epiphos dries giving a glossy, clear, hard surface allowing visual inspection prior to application of finish coats.

and...

Tergophos is a phosphoric acid based cleaner, containing detergents, solvents and a corrosion inhibitor, which is applied either by brush, immersion or spray for rust control and the removal of dirt, tarnish and other insoluble metallic deposits. Tergophos is carefully formulated to penetrate quickly, convert rust and form a stable chemical layer to act as a bond for paint and to control rusting. Especially effective prior to painting aluminium, galvanised iron and mild steel.

Latter is bloody brilliant for cleaning aluminium.
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Old 11-06-2016, 05:19 PM
ojh ojh is offline
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We reactivate the acid with another coat of acid and then wipe while wet (don't let the ospho dry) with water, we've done it the next day after applying the first coat. Th finish is all nice and uniform.
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Last edited by ojh; 11-06-2016 at 05:21 PM. Reason: clarify
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Old 11-07-2016, 02:42 AM
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Gojeep Gojeep is offline
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Quote:
Originally Posted by ojh View Post
We reactivate the acid with another coat of acid and then wipe while wet (don't let the ospho dry) with water, we've done it the next day after applying the first coat. Th finish is all nice and uniform.
What ratio acid to water are you using and how long before you wipe it off again while it is still wet please?
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