Challenging the Performance Myth of Inorganic Zinc Rich vs Organic Zinc Rich PrimersAbstractZinc rich primer coatings both organic and inorganic are extensively used in highly corrosive environments and they are part of a high performance coating system in the Protective Coatings Industry. During the 60’s and the 70’s zinc rich epoxy primers dominated the market. Later zinc ethyl silicate primers took over this role but nowadays it appears as if zinc epoxy primers have made a comeback. Some of the advantages of zinc epoxies compared to zinc silicates are the less demanding curing conditions (epoxies will cure at low humidity) they are easier to overcoat and they are less demanding to substrate preparation prior to application. Zinc epoxies are typically formulated with high loads of zinc dust also zinc epoxies are mechanically stronger meaning that in the real life over thickness is less problematic for new generation of epoxies than for zinc silicates that can fail by mud cracking. According to ISO 12944 a zinc rich coating contains more than 80% zinc by weight in the dry film.The protecting mechanism of zinc rich coatings is believed mainly to be based on galvanic protection provided by the zinc dust in the paint. When a coating system containing a zinc rich primer is exposed to a corrosive environment rust creep and blistering are amongst the most important failure mechanisms to be considered. Many accelerated exposures will not within their exposure time show the defects visually on intact coated surfaces. Therefore behaviour of the coatings involving artificially made damages i.e. scores are given significant considerations in the development of efficient anti-corrosive primers. Many prequalification tests (e.g. ISO 12944-6 ISO 20340 NORSOK M501 Rev.6) are based amongst others on rust creep and blistering as well as detachment from scores.The increasing demands on the performance of zinc rich primers (low rust creep and better mechanical properties) has focussed attention on maximizing the utilization of the zinc dust in the paint. In addition to this the recent developments in the market prices of zinc dust suggest opportunities for new developments in this area. Is it now possible to achieve the same level of corrosion protection with an organic binder containing the same level of zinc dust as its inorganic equivalent. Previously Zinc rich epoxy coatings required higher levels of zinc dust to achieve the same level of corrosion protection as their inorganic zinc silicate counteparts.All these benefits can be achieved with innovative zinc rich epoxies with special fillers and activators which are specifically designed to provide extreme corrosion protection durability productivity and improved mechanical performance.The purpose of this paper is to describe the protecting mechanisms of a new generation of zinc rich primers with enhanced protection vs inorganic zinc rich primers. The performance properties of the new generation primer have been proven with real results from different corrosion tests (ISO 12944-6 Salt Spray Test according to ISO 9227 NACE Cracking Test TM0304) vs inorganic zinc rich primers which will be presented as well.Key words: Zinc epoxy active fillers ISO 12944 ISO 9227 NACE TM0304 Corrosion Protection Rust Creep Zinc silicate NORSOK M501 Rev 6 ISO 20340