sudhir

Topic: What will be the adequate pretreatment on G.I. substrate before powder

Please kindly inform adequate Pre-treatment on Galvanised substrate before powder coating?

At present we are following alkaline cleaner, water rinse,hot air dry followed powder coating & required baking. Film tested for bend & other Mechanical test & found as passing, but after day or two days film gets failure in bend test at 6 mm also. Kindly suggest.

ChemSlinger

Re: What will be the adequate pretreatment on G.I. substrate before powder

Sudhir,

Instead of using a straight alkaline cleaner for the first stage, I would recommend a good cleaner/phosphatizer combination, followed by a clean rinse, then dry and paint. The cleaner/phosphatizer reacts with the metal creating a greater surface area for the paint to adhere. This process is very common with aluminum and galvanized substrates in the powder coating industry.

EnviroServe Chemicals, Inc. has everything you need on the chemical end to get you the proper results. Please give us a call if you would like to talk further about your process and some possible solutions.

Thanks,

EnviroServe Chemicals, Inc.

(910) 892-1791

ChemSlinger's Website

sudhir

Re: What will be the adequate pretreatment on G.I. substrate before powder

Kindly inform chemical application method (Dip / Spray) & it's working parameter.

As well as what will be the measurement of good quality treatment ?

If possibel Technical Data Sheet of the same on mail ID sudhirbhegade@msn.com

ChemSlinger

Re: What will be the adequate pretreatment on G.I. substrate before powder

The chemical application will work for either a dip/immersion or a spray washer / spray wand.

A good cleaner/iron phosphate should be used at a concentration from 2-4% with a pH level of 3.5-5.0. One of our best cleaner/iron phosphate products for spray washers is our EnviroPhos 2283. This is a multi-metal safe product that gives good adhesion and coating weights. I'll send you the TDS for it.

EnviroServe Chemicals, Inc.

(910) 892-1791

ChemSlinger's Website

skip

Re: What will be the adequate pretreatment on G.I. substrate before powder

Not that the following is any recommendation to pretreatment of galvanized steel.

Do these descriptions sound about right, it has been so long I forget. Thanx. skip.

Zinc plating is electroplating where the parts are cathodic [-] drawing the zinc from [+] anodes of zinc; appling a thin smooth layer for decorative and protective uses.

Galvanizing is a system where zinc is melted onto a molten form and the parts are fluxed and dipped into the molten bath and then removed to cool. This usually applies a thicker and rougher finish of great resistance to rust.

This galvanizing [highway guard rails] is a self sacrificing finish which means that 'it'...the galvanizing self oxidizes instead of the part. Any painted coating on the galvanized work degrade, and usually chalk off.

Zinc electro plating is also a form of galvanization which is commonly called electogalvanization. Guard rails and buckets are usually hot dip galvanized to get a thicker deposit of the sacrificial zinc. Unlike tin plating, a scratch down to the steel will not cause rust until the zinc in the area is all sacrificed. In fact, the zinc will oxidize and in many cases heal over the scratch to further prevent parent metal corrosion. There is another safer process where the zinc is essentially powder coated onto a panel and then heated to bond the zinc. This doesn't weaken the metal to extent that electrogalvanizing does and is a less hazardous process that produces a finish with great tooth for paint to stick to.

skip.

Last edited by skip (12/28/2009 - 09:20 PM)

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