A Complete Range Of Metal Cleaning
And Surface Treatment Solutions


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June 8, 2017

Problems caused by conventional cleaning and metal pretreatment systems

metal treatment

Exploring a new solution to the problems caused by conventional cleaning and metal pretreatment systems in product finishing.

EnviroTech Surface Technologies looks at some of the traditional problems associated with solvent and aqueous degreasing prior to painting and powder coating and explains how the DriPHOS® option can offer a viable alternative to conventional processes. The DriPHOS® surface treatment process has evolved to produce a revolution in metal finishing.

DriPHOS

DriPHOS® the start of a great finish

Traditionally jobbing painters and/or manufacturers of parts who have to subsequently degrease and then paint or powder coat have had the same problems that they have learnt to live with. These include: reject rates of between 3 – 8% after painting; residues of particulate that require further manual wiping after degreasing and prior to painting; paint schemes lifting or blistering; corrosion forming under painted areas; parts slowing down the production because the drying oven takes an excessively long time to dry sufficiently; or parts simply going rusty during the dwell time between cleaning and subsequent painting.

Finally, when using conventional solvents, long dwell times whilst the components cool down to a temperature that can take the paint prior to curing in the oven. More recently, classification of Trichloroethylene has also caused concern. These and others must sound familiar to you.

 

What causes this to happen?
Obviously a lot of factors come to mind but generally they fall into four main areas as follows:

● Inadequate degreasing
● Residual contamination
● Retained moisture or solvent under the surface of crimped areas, spot welds and seams etc
● No protection from rusting whilst awaiting painting

Why does this happen?
To try to simplify this we have broken it down into aqueous cleaning and solvent cleaning with some of the reasons under each of the four headings above as follows:

MAIN CAUSES AQUEOUS METHOD SOLVENT METHOD
INADEQUATE DEGREASING – Solution out of spec or contaminated
– Temperature to low
– Rinses contaminated
– Filters blocked
– Only vapour used
– Poor loading
– Wrong solvent used
– Solvent turned acidic
RESIDUAL CONTAMINATION – Wrong product used
– Contaminated rinse water
– Poor loading
– Particulate left by vapour
– Solvent turned acidic
– Poor loading
RETAINED MOISTURE – Insufficient time to dry
– Poor loading
– Parts not designed to drain properly
– Solvent trapped in parts
– Parts not designed to drain properly
NO INTERIM PROTECTION – No corrosion inhibitor
– Residual contamination
– Solution out of specification
– High temperature draws moisture from atmosphere

All of the above are avoidable but may mean tighter controls and different process methods are required. The way the components are loaded is vitally important as overlapping can prevent access for both the aqueous and solvent processes. Unfortunately most paint shop managers will not feel they can afford the time to load more carefully even when they realise the advantages.

What can be used as an alternative?
The answer is DriPHOS®  the new  single tank surface treatment process.

What is DriPHOS®?
It is a solvent-based degreasing and pretreatment process. Based on a well-tried and tested blend of solvents and sophisticated additives and surface activators, DriPHOS® really is the quickest, most economical answer to degreasing and surface treatment  problems. Operating at only 42°C the parts come out of the process totally clean, dry and with a crystalline primed surface to enhance painting and cool enough to handle or to go straight into the paint area. One tank is all that is needed.

How does it work?
It works by a combination of vapour and immersion stages in one tank.  After initial degreasing in the vapour, parts are then immersed into the DriPHOS® boiling sump where the residual oils and particulate is removed and the phosphate coating is chemically bonded to the surface of all of the parts. After a mini rinse/ final vapour stage the parts are left in the freeboard area for a short time before coming out of the tank totally clean, dry and with a protective surface coating. This gives an excellent bond for subsequent painting operations, with minimal reject rates due to delamination or undercoat staining. . The crystalline coating gives inter-stage protection until painting is needed. Another bonus is the colour change of the metal surface  gives a visual indication of quality. The process can be used on steel or aluminium components or mixed metal components or fabrications. For steel parts a total process time can be as little as 3 – 5 minutes. Aluminium parts will be 1 –2 minutes. Bath life averages 2 years. One tank needs little space and uses only small amounts of energy. A very fast, economical and simple to run process.

Why doesn’t everyone use it?
The truth is that, like all processes, it will not work for every application but a quick visit by one of our DriPHOS specialists will confirm if it would be a practical solution to improve the finish on your products. We back this up with full technical support, solvent monitoring, equipment advice, operator training, and a lot more.

For information or advice on the use of DriPHOS or to arrange validation trials at the new test centre or visits by product specialists, appointments can be made by phone or through the product website www.metal-treatment.com.

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March 27, 2017

Degreasing and rust prevention is essential for stored metal parts

metal treatment

How degreasing and rust prevention is essential for stored metal parts in flexible manufacturing processes.

Flexible batch production for variable numbers and colours of finished products is very difficult to achieve when producing fabricated items in mild steel sheet due to storage of the unpainted parts being subject to rusting and corrosion when processed by conventional water based processes. This paper describes a typical manufacturing cycle for office and educational equipment where rust free storage allows JIT deliveries.

DriPHOS

To satisfy contracts to produce a wide range of metal cabinets, chests, and lockers in many different sizes with a range of cabinets and shelving, all in different colours, for the education sector which have to be delivered within 7 days, needs very careful production planning. It is necessary to stock drawers, tops and backs, punched, laid flat, unpainted, and then produce sides to order. Three pieces of equipment allow successful operation of this production process. A CNC controlled sheet metal folding and bending centre an automatic DriPHOS combined degreasing and metal pre-treatment process tank and a fast colour change powder or paint coating plant and an oven.

In the case of the bending operation, a stock of pre-punched blanks is carried which when a ‘rush’ order is received the automated CNC folding system, will typically produce the end folds in a pair of sides, within ten minutes – without disrupting normal planned production.

The DriPHOS pre-treatment operation is critical to achieving these very tight schedules. A fully integrated CAD/CAM system enables a product to be taken from concept to finished item. Manufacture of batches of storage cabinets from tens to 500 off will need up to 20,000 items of sheet metal work and shelving. Batches of machined parts which must be stored, for long periods, can be transferred to the pre-treatment cell and loaded into a basket or jig, positioned to allow good circulation of DriPHOS solution around the parts.

The loaded basket is placed onto an automated handling system to raise and lower work within the enclosed process tank to a defined cycle. The DriPHOS process is similar to vapour degreasing and requires minimal space as only one tank is involved rather than the altern ative multi tank water based systems. Held in the vapour zone above the boiling DriPHOS solution, vapour condenses on the components until the temperature equalises at 31°C. This degreases the surfaces and removes loose dirt as it is flushed away by the condensed DriPHOS. After immersion in the solution for 2- 3 minutes, the basket/ jig is raised into the vapour zone where it is spray-rinsed for 30 seconds with cooled DriPHOS distillate to remove traces of process liquid. Residual condensate flash evaporates as the basket is slowly removed from the tank. The whole cycle takes only five minutes.

DriPHOS enables finished parts to be degreased, pre-treated and protected prior to assembly. Any other process would have to see parts painted in no more than an hour after treatment during which time rusting may occur. DriPHOS on the other hand presents a physical barrier against moisture, inhibiting rust and corrosion. Parts can be assembled and painted up to a year after treatment.
Whether direct from the degreasing and pre-treatment cell or from pre-treated stock from storage, cabinet ‘carcases’ are assembled, TIG welded and ‘jigged up’, along with shelving, doors etc on a motorised overhead carousel. They progress into an automated paint or powder booth with two open stations, for manual spray operations, for operators to ensure all internal corners are covered. The complex crystal structure applied by the DriPHOS process uses thin layer technology (TLT) to produce a crystalline bond that is integral with the metal substrate, increasing the surface area and providing an excellent key for paint, powder and other finishes.

Painted units are passed through ovens from where final assembly sees shelves, doors, handles etc fitted. Finished units can be packaged and despatched the same day. Providing metal storage systems from stock would not be possible without DriPHOS as a pre-treatment solution for rust and corrosion free storage of the sheet metal parts.

For information or advice on the use of DriPHOS or to arrange validation trials at the new test centre or visits by product specialists, appointments can be made by phone or through the product website www.metal-treatment.com.

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EnviroTech Surface Technologies
A Complete Range Of Metal Cleaning And Surface Treatment Solutions

EnviroTech Europe Ltd
100a High Street
Hampton
Middlesex
United Kingdom TW12 2ST

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