The influence of electroless plated chromium on printing properties of aluminium offset printing plate

A method for the improvement of the printing properties of offset printing forms is presented. Specimens of technical aluminum were electrochemically roughened and treated in different alkaline solutions of chromium chloride in order to chemically deposit a chromium layer. The composition of the surface layer was investigated by EDAX. Chromium was found on the specimens that had been treated in an alkaline solution of chromium chloride, while no chromium was found on chemically untreated specimens or on specimens that had been treated in an alkaline solution without chromium chloride. The spectral reflectance from treated and non-treated specimens was also measured. The chromium-treated specimens were brighter than the non-chromium-treated ones. The wettability of the chromium- treated samples was compared with the wettability of the non-chromium treated samples by measuring the contact angle with water and the wetted area. The chromium-treated samples showed increased wettability compared with the non-chromium-treated samples.A printing test was performed under real printing conditions. Control prints was analyzed densitometrically and statistically. The chromium-treated printing forms gave clearer prints than the non-chromium-treated printing forms under all printing conditions. Prikazan je metod za poboljsanje svojstava stamparskih formi za ofset stampu. Uzorci tehnickog aluminijuma su elektrohemijski nahrapavljeni i tretirani razlicitim rastvorima u cilju ispitivanja mogucnosti hemijskog talozenja hroma na aluminijumu. Sastav povrsinskog sloja obradjivanih uzoraka odredjen je EDAX-om. Prisustvo hroma dokazano je na uzorcima koji su tretirani alkalnim rastvorima koji su sadrzali Cr3+ jone, dok na uzorcima koji su tretirani rastvorima bez prisustva hromnih jona prisustvo hroma nije potvrdjeno. Izmerena je spektralna refleksija hromiranih i nehromiranih uzoraka. Izvrseno je poredjenje kvasljivosti hromiranih i nehromiranih uzoraka. Kvasljivost nehromiranih uzoraka uporedjena je sa kvasljivoscu hromiranih uzoraka merenjem kontaktnog ugla sa vodom kao i okvasene povrsine. Konstatovano je da se hromirani uzorci bolje kvase od nehromiranih. Eksperimentalno stampanje je izvrseno pod realnim uslovima. Kotrolni otisci analizirani su na osnovu denzitometrijskih merenja i statistickom analizom skenirane slike. Kontrolni otisci nacinjeni pomocu hromiranih formi bili su cistiji od kontrolnih otisaka nacinjenih nehromiranim formama pod svim uslovima stampanja, a pose