Ongoing Development Project Update: January 2007 ISSUE 1
Chrome as a constituent in coating systems is becoming more and more high profile, particularly with the advent of the environment lobby, and such legislation as WEE and REACH. Of note is the recent decision to eliminate chrome containing systems taken by the US DoD.
Indestructible Paint, as an ISO14001 approved company, considered the continued use of chrome some years ago, and has a policy of keeping its use and/or removal high on its development and marketing agenda. Our ongoing commitment is the manufacture and supply of “Low Environmental Impact” products wherever feasible and practical.
As a result, we have been continuously evolving various policies to deal with chrome containing materials. Some of those decisions follow:-
Over five years ago, a decision was made by Indestructible to discontinue the use of chrome and lead containing pigments in all coloured top coats, including the IP9064 epoxy range and the IP6 polyurethane range.
This policy has been rigorously followed ever since, even though chrome free pigments may not provide equivalent opacity, and may also have cost implications.
As a result, Indestructible Paint is proud to say that we have not used chrome containing pigments in any of our top coat lists for in excess of five years.
Pre-treatments systems for aluminium, magnesium, and in some cases steel, and their alloys have traditionally employed chrome containing solutions, typically the Alochrome type. In most instances pre-treatment products are supplied not by coatings manufacturers but by chemical companies.
We see the use of metal pre-treatments as integral with the subsequent primer and top coat schemes, and have developed, and are continuing to refine a chrome free pre-treatment process. Please see our separate Technical Data Sheets entitled “Cleaners and Pre-treatment Systems for Aluminium and Magnesium”.
Etch Primers, like pre-treatment systems, can fall under Aerospace, Defence or General Industrial purposes. One and two pack systems are common throughout the coatings industry.
The two pack system used throughout the aerospace and defence industries must meet either BSX32 or De-Stan 80-15. However both these standards specify the use of chrome anti-corrosive pigments, and there is therefore no possibility that a chrome free coating can comply with these standards.
However, our work has enabled us to- formulate a chrome free system, based on a proprietary “phosphate” anti-corrosive pigment that will meet the performance requirements of these aerospace and defence specifications. This is now being used in marine and general industrial applications where the standards are not part of the coating contract.
Please see our information sheet on IP3-4853/4
We also produce chrome free single pack etch primers/conversion coatings, which are used in general industrial and automotive projects. For information please refer to our data sheet on 40012/40018/
Across the various industry sectors we supply, there are several ranges of primer systems, including, air drying, cold cure and baking products.
The most widely used ranges are:
In the majority of cases, all these grades of primers have been formulated using zinc chromate; barium chromate, zinc tetroxy chromate, strontium chromate or even blends as the anti-corrosive pigment.
In the UK most of the specifications based around these products still apply. For instance the 2 component epoxy anti-corrosive primer for airframe and ancillaries still calls up BSX33(BS2X33) which specify the use of chromate, whilst the Rolls Royce specification for baking epoxy (MSRR 9226) similarly specifies the use of chromate anti-corrosive pigments.
However in the USA and Europe, there are active moves to chrome free versions of all these primers and we have conducted much detailed development work into chrome free alternatives.
Our work was initially concentrated on two component epoxy resin systems, but the alternative pigments evaluated can of course and have been used in other resin bases.
About seven years ago, our first initial choice of chrome free anti-corrosive pigment was zinc phosphate. Whilst this showed acceptable corrosion resistance in general industrial and light marine use, the performance did not approach the requirements of most aero engine specifications, and certainly not airframe.
It is however still widely used in leisure marine and industrial applications; see our information on alkyd systems PF25773-R2 and 32013-R1, and 2 pack low VOC epoxy IP2-ZNP.
New proprietary phosphate based pigments began to be developed, and after much research and technical testing, we produced a range of chrome free 2 pack epoxy primers to meet the corrosion resistance and chemical resistance requirements of most major aero engine manufacturers. It is worth noting that each manufacturer has differing performance requirements on heat and chemical resistance, but all look for in excess of 2000 hours HSS to ASTM B-117. Please contact our technical team to discuss which of these products best suits your requirements.
The ranges of 2 pack epoxies include:
It is worth noting that both IP714 types and IP3-6500/6600 are not only chrome free but very low VOC, and HAPS solvent free.
Please refer to the relevant technical data sheets for full information.
Utilising this new pigment technology, new versions of the baking epoxy system were produced, which have been approved by several European aero engine and aerospace manufacturers, including Turbomeca (LB 569) and Eurocopter (ECS 2178). Please view our technical data on IP985-6500.
Indestructible believe that there are still further improvements to be made, and are currently evaluating the latest available anti-corrosive pigments. We are hopeful that from this ongoing work, we will be able to produce primer systems that surpass the performance of chrome containing versions.
We are aware of the interest in chrome free anti-corrosive systems, and the proposed new specification for airframe use (BS.EN 2436). We also have ongoing dialogues with several manufacturers which will involve ongoing technical testing.
For the very latest information on the removal of chrome from performance coatings systems please do contact our technical department.
Please contact Indestructible Paint to follow up on any issues raised on this page.
